<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2024 Workiva-->
<!--r:4d33bb0f-2240-47e2-8a7c-31d30d14abcd,g:233f4962-8cc0-4bdc-ab10-02581606db1e-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.gentex.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFSHAREHOLDERSINVESTMENT" xlink:type="simple" xlink:href="gntx-20240331.xsd#UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFSHAREHOLDERSINVESTMENT"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/UNAUDITEDCONDENSEDCONSOLIDATEDSTATEMENTSOFSHAREHOLDERSINVESTMENT" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_a076dd6f-0715-45fa-8c06-adc8c70b64d5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_8d4f1e3f-ecb8-4974-b100-00c3cf27e410" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_a076dd6f-0715-45fa-8c06-adc8c70b64d5" xlink:to="loc_us-gaap_StatementTable_8d4f1e3f-ecb8-4974-b100-00c3cf27e410" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_ab33f9f5-ab90-4616-b3a4-3dd18c1abb83" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_8d4f1e3f-ecb8-4974-b100-00c3cf27e410" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_ab33f9f5-ab90-4616-b3a4-3dd18c1abb83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_ab33f9f5-ab90-4616-b3a4-3dd18c1abb83_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_ab33f9f5-ab90-4616-b3a4-3dd18c1abb83" xlink:to="loc_us-gaap_EquityComponentDomain_ab33f9f5-ab90-4616-b3a4-3dd18c1abb83_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_54a17afe-8800-4496-9f51-5ac88a520be1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_ab33f9f5-ab90-4616-b3a4-3dd18c1abb83" xlink:to="loc_us-gaap_EquityComponentDomain_54a17afe-8800-4496-9f51-5ac88a520be1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_9ee7ca6d-5cd2-4c72-bb95-2d0a5b0a8a68" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_54a17afe-8800-4496-9f51-5ac88a520be1" xlink:to="loc_us-gaap_CommonStockMember_9ee7ca6d-5cd2-4c72-bb95-2d0a5b0a8a68" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_cfd0d06c-7469-451d-90b1-8035b860a863" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_54a17afe-8800-4496-9f51-5ac88a520be1" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_cfd0d06c-7469-451d-90b1-8035b860a863" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_1f30e9b7-10ac-40ce-98f8-4c83fbb0203b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_54a17afe-8800-4496-9f51-5ac88a520be1" xlink:to="loc_us-gaap_RetainedEarningsMember_1f30e9b7-10ac-40ce-98f8-4c83fbb0203b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_2184eaa8-c8e0-4127-8955-d384b9dd0dcc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_54a17afe-8800-4496-9f51-5ac88a520be1" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_2184eaa8-c8e0-4127-8955-d384b9dd0dcc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93da3b17-c6ea-418b-8c35-58163f66e46d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_a076dd6f-0715-45fa-8c06-adc8c70b64d5" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93da3b17-c6ea-418b-8c35-58163f66e46d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_7527d336-b571-4932-be1b-1b13dbccaa6e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93da3b17-c6ea-418b-8c35-58163f66e46d" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_7527d336-b571-4932-be1b-1b13dbccaa6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_048c7f88-b8d8-46a4-b403-955c5e9bd91e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93da3b17-c6ea-418b-8c35-58163f66e46d" xlink:to="loc_us-gaap_StockholdersEquity_048c7f88-b8d8-46a4-b403-955c5e9bd91e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_f3bf2abc-274c-4bc5-a4b8-a4dd3783299b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93da3b17-c6ea-418b-8c35-58163f66e46d" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_f3bf2abc-274c-4bc5-a4b8-a4dd3783299b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_d83af3b5-1b88-49d3-81fd-97c81ee52a00" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93da3b17-c6ea-418b-8c35-58163f66e46d" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_d83af3b5-1b88-49d3-81fd-97c81ee52a00" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_16849475-7013-4619-9cda-bdfea8414777" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93da3b17-c6ea-418b-8c35-58163f66e46d" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_16849475-7013-4619-9cda-bdfea8414777" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_8fb63df5-3c59-44b5-87a3-180c1da3dd1b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93da3b17-c6ea-418b-8c35-58163f66e46d" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_8fb63df5-3c59-44b5-87a3-180c1da3dd1b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_a0d473fe-0529-4c1f-8cab-d2cce276e23e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93da3b17-c6ea-418b-8c35-58163f66e46d" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_a0d473fe-0529-4c1f-8cab-d2cce276e23e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_fe613abf-7d86-4065-9888-cf8535642e24" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93da3b17-c6ea-418b-8c35-58163f66e46d" xlink:to="loc_us-gaap_DividendsCommonStockCash_fe613abf-7d86-4065-9888-cf8535642e24" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_39c91117-25bd-49b6-8bd1-eeda1bf0f6f9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93da3b17-c6ea-418b-8c35-58163f66e46d" xlink:to="loc_us-gaap_NetIncomeLoss_39c91117-25bd-49b6-8bd1-eeda1bf0f6f9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_9c142012-37dc-4bf7-878e-f9eee0046749" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_93da3b17-c6ea-418b-8c35-58163f66e46d" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_9c142012-37dc-4bf7-878e-f9eee0046749" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_57a77342-0b13-4d5f-855e-3de2d519ddcc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_adace95c-5643-427d-983b-847567ec2838" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#GoodwillandOtherIntangibleAssetsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10482ee-6ad1-45a8-8b5d-fc2d1b7cc9dd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_f8cb27e5-4dc4-4085-ac05-fcb8f75b5569" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10482ee-6ad1-45a8-8b5d-fc2d1b7cc9dd" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_f8cb27e5-4dc4-4085-ac05-fcb8f75b5569" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_5b558eca-b394-47ba-9222-e1843411b6ed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_f8cb27e5-4dc4-4085-ac05-fcb8f75b5569" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_5b558eca-b394-47ba-9222-e1843411b6ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5b558eca-b394-47ba-9222-e1843411b6ed_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5b558eca-b394-47ba-9222-e1843411b6ed" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5b558eca-b394-47ba-9222-e1843411b6ed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_06e3cef2-9b68-4f52-930d-2761420b6b66" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5b558eca-b394-47ba-9222-e1843411b6ed" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_06e3cef2-9b68-4f52-930d-2761420b6b66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_HomeLinkMember_544913b0-98cd-4f76-b303-83f6a70547a1" xlink:href="gntx-20240331.xsd#gntx_HomeLinkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_06e3cef2-9b68-4f52-930d-2761420b6b66" xlink:to="loc_gntx_HomeLinkMember_544913b0-98cd-4f76-b303-83f6a70547a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_VaporsensIncMember_10ded409-7820-4e99-a7b1-e7d5cc4cc7b4" xlink:href="gntx-20240331.xsd#gntx_VaporsensIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_06e3cef2-9b68-4f52-930d-2761420b6b66" xlink:to="loc_gntx_VaporsensIncMember_10ded409-7820-4e99-a7b1-e7d5cc4cc7b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AirCraftGlassProductionBVMember_18ea0c55-c426-42a2-8ca3-e90d07541712" xlink:href="gntx-20240331.xsd#gntx_AirCraftGlassProductionBVMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_06e3cef2-9b68-4f52-930d-2761420b6b66" xlink:to="loc_gntx_AirCraftGlassProductionBVMember_18ea0c55-c426-42a2-8ca3-e90d07541712" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ArgilIncMember_3e6af1d7-521d-4875-81a0-0e62817dea27" xlink:href="gntx-20240331.xsd#gntx_ArgilIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_06e3cef2-9b68-4f52-930d-2761420b6b66" xlink:to="loc_gntx_ArgilIncMember_3e6af1d7-521d-4875-81a0-0e62817dea27" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_GuardianOpticalTechnologiesMember_b7e7519c-2af5-42fd-acbb-ef35d98863ee" xlink:href="gntx-20240331.xsd#gntx_GuardianOpticalTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_06e3cef2-9b68-4f52-930d-2761420b6b66" xlink:to="loc_gntx_GuardianOpticalTechnologiesMember_b7e7519c-2af5-42fd-acbb-ef35d98863ee" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ESightCorporationMember_ca2f79b8-3e70-44d7-ac65-05c22d4ecc8d" xlink:href="gntx-20240331.xsd#gntx_ESightCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_06e3cef2-9b68-4f52-930d-2761420b6b66" xlink:to="loc_gntx_ESightCorporationMember_ca2f79b8-3e70-44d7-ac65-05c22d4ecc8d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_47b7cc79-58c5-43f4-a5b4-807566bd1691" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_f8cb27e5-4dc4-4085-ac05-fcb8f75b5569" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_47b7cc79-58c5-43f4-a5b4-807566bd1691" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47b7cc79-58c5-43f4-a5b4-807566bd1691_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_47b7cc79-58c5-43f4-a5b4-807566bd1691" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_47b7cc79-58c5-43f4-a5b4-807566bd1691_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1b4758ca-b863-4d50-9ddd-fa095ba89a9a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_47b7cc79-58c5-43f4-a5b4-807566bd1691" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1b4758ca-b863-4d50-9ddd-fa095ba89a9a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_PatentsAndOtherIntangibleAssetsMember_da338d05-de1e-42db-8562-3244fa4ecf58" xlink:href="gntx-20240331.xsd#gntx_PatentsAndOtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_1b4758ca-b863-4d50-9ddd-fa095ba89a9a" xlink:to="loc_gntx_PatentsAndOtherIntangibleAssetsMember_da338d05-de1e-42db-8562-3244fa4ecf58" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_360d9f92-8c2b-4a1b-ae8b-6a5a6d429cb3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10482ee-6ad1-45a8-8b5d-fc2d1b7cc9dd" xlink:to="loc_us-gaap_Goodwill_360d9f92-8c2b-4a1b-ae8b-6a5a6d429cb3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAcquiredDuringPeriod_49b4e54c-5c1e-485b-8acf-bc29b69386ee" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GoodwillAcquiredDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10482ee-6ad1-45a8-8b5d-fc2d1b7cc9dd" xlink:to="loc_us-gaap_GoodwillAcquiredDuringPeriod_49b4e54c-5c1e-485b-8acf-bc29b69386ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_114fb8ca-5bba-4444-a13c-e856d572c3f3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10482ee-6ad1-45a8-8b5d-fc2d1b7cc9dd" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_114fb8ca-5bba-4444-a13c-e856d572c3f3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_99ef251c-2fb5-4d57-b720-3f4e52b2a3be" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10482ee-6ad1-45a8-8b5d-fc2d1b7cc9dd" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_99ef251c-2fb5-4d57-b720-3f4e52b2a3be" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_84410819-e800-4b1d-8df4-0c2217062d09" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10482ee-6ad1-45a8-8b5d-fc2d1b7cc9dd" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_84410819-e800-4b1d-8df4-0c2217062d09" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_83d438fe-463a-41b3-a0cd-a1b31c06a54c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10482ee-6ad1-45a8-8b5d-fc2d1b7cc9dd" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_83d438fe-463a-41b3-a0cd-a1b31c06a54c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_2627db89-72e2-4473-8ade-aec5916aae8a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10482ee-6ad1-45a8-8b5d-fc2d1b7cc9dd" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_2627db89-72e2-4473-8ade-aec5916aae8a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_4df345e0-5494-4535-9bc6-29d325d1903e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10482ee-6ad1-45a8-8b5d-fc2d1b7cc9dd" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_4df345e0-5494-4535-9bc6-29d325d1903e" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_7f582e57-ee41-4969-9d35-99a3c6744cf9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_3bfceeb5-c5c4-448c-bf82-8f6053e67225" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_7f582e57-ee41-4969-9d35-99a3c6744cf9" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_3bfceeb5-c5c4-448c-bf82-8f6053e67225" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_33239ba6-dffd-49c1-952f-ce5d9299adc9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_3bfceeb5-c5c4-448c-bf82-8f6053e67225" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_33239ba6-dffd-49c1-952f-ce5d9299adc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_33239ba6-dffd-49c1-952f-ce5d9299adc9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_33239ba6-dffd-49c1-952f-ce5d9299adc9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_33239ba6-dffd-49c1-952f-ce5d9299adc9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_aa733711-29ee-4451-b84b-a7a2b7eb3081" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_33239ba6-dffd-49c1-952f-ce5d9299adc9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_aa733711-29ee-4451-b84b-a7a2b7eb3081" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentsMember_7df76472-ff4a-4050-bc15-8f33f5bafbcc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PatentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_aa733711-29ee-4451-b84b-a7a2b7eb3081" xlink:to="loc_us-gaap_PatentsMember_7df76472-ff4a-4050-bc15-8f33f5bafbcc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_060cbc9a-1817-4437-8541-e56fc8c58e6e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_aa733711-29ee-4451-b84b-a7a2b7eb3081" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_060cbc9a-1817-4437-8541-e56fc8c58e6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_76135d28-4f8e-4e15-b200-e2486baafa75" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIntangibleAssetsMember_060cbc9a-1817-4437-8541-e56fc8c58e6e" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_76135d28-4f8e-4e15-b200-e2486baafa75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerContractsMember_9445169c-cb15-410f-a9dc-2bc9eec505bd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CustomerContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIntangibleAssetsMember_060cbc9a-1817-4437-8541-e56fc8c58e6e" xlink:to="loc_us-gaap_CustomerContractsMember_9445169c-cb15-410f-a9dc-2bc9eec505bd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_429e6e4d-b893-4043-a85c-eb546429a269" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIntangibleAssetsMember_060cbc9a-1817-4437-8541-e56fc8c58e6e" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_429e6e4d-b893-4043-a85c-eb546429a269" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_PatentsAndOtherIntangibleAssetsMember_71806721-7ed8-40ad-894a-f9df1f773a87" xlink:href="gntx-20240331.xsd#gntx_PatentsAndOtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_aa733711-29ee-4451-b84b-a7a2b7eb3081" xlink:to="loc_gntx_PatentsAndOtherIntangibleAssetsMember_71806721-7ed8-40ad-894a-f9df1f773a87" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_6f9d0f29-5fbf-43bb-8ec8-b1f7b828b2c4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_3bfceeb5-c5c4-448c-bf82-8f6053e67225" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_6f9d0f29-5fbf-43bb-8ec8-b1f7b828b2c4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_6f9d0f29-5fbf-43bb-8ec8-b1f7b828b2c4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_6f9d0f29-5fbf-43bb-8ec8-b1f7b828b2c4" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_6f9d0f29-5fbf-43bb-8ec8-b1f7b828b2c4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_41bcd00a-2d56-4508-b9f4-4c09af95eb1e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_6f9d0f29-5fbf-43bb-8ec8-b1f7b828b2c4" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_41bcd00a-2d56-4508-b9f4-4c09af95eb1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_6564ad01-53bc-495b-a54d-491bfe6a91db" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_41bcd00a-2d56-4508-b9f4-4c09af95eb1e" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_6564ad01-53bc-495b-a54d-491bfe6a91db" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LicensingAgreementsMember_7be6efd1-7c47-439b-b3c8-2085ddf69110" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LicensingAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_41bcd00a-2d56-4508-b9f4-4c09af95eb1e" xlink:to="loc_us-gaap_LicensingAgreementsMember_7be6efd1-7c47-439b-b3c8-2085ddf69110" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InProcessResearchAndDevelopmentMember_077359ac-475f-4d36-87d7-d7910e43bfd0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InProcessResearchAndDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_41bcd00a-2d56-4508-b9f4-4c09af95eb1e" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_077359ac-475f-4d36-87d7-d7910e43bfd0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_74e58256-d6ac-46c9-8309-2312b3a6dade" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_3bfceeb5-c5c4-448c-bf82-8f6053e67225" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_74e58256-d6ac-46c9-8309-2312b3a6dade" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_74e58256-d6ac-46c9-8309-2312b3a6dade_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_74e58256-d6ac-46c9-8309-2312b3a6dade" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_74e58256-d6ac-46c9-8309-2312b3a6dade_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_807cd573-a3ed-4527-9ea7-1b9924238b31" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_74e58256-d6ac-46c9-8309-2312b3a6dade" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_807cd573-a3ed-4527-9ea7-1b9924238b31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_HomeLinkMember_e48ebb0e-87c8-4310-9ad6-22d730dde332" xlink:href="gntx-20240331.xsd#gntx_HomeLinkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_807cd573-a3ed-4527-9ea7-1b9924238b31" xlink:to="loc_gntx_HomeLinkMember_e48ebb0e-87c8-4310-9ad6-22d730dde332" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ESightCorporationMember_f6f6c472-4a05-4d58-a1d1-09ac05eb4c9f" xlink:href="gntx-20240331.xsd#gntx_ESightCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_807cd573-a3ed-4527-9ea7-1b9924238b31" xlink:to="loc_gntx_ESightCorporationMember_f6f6c472-4a05-4d58-a1d1-09ac05eb4c9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_VaporsensIncMember_c0f06700-1567-453b-bff8-66f3c9f1b23e" xlink:href="gntx-20240331.xsd#gntx_VaporsensIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_807cd573-a3ed-4527-9ea7-1b9924238b31" xlink:to="loc_gntx_VaporsensIncMember_c0f06700-1567-453b-bff8-66f3c9f1b23e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ArgilIncMember_3383a4b2-b581-4a45-8e8e-491cc5670a2f" xlink:href="gntx-20240331.xsd#gntx_ArgilIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_807cd573-a3ed-4527-9ea7-1b9924238b31" xlink:to="loc_gntx_ArgilIncMember_3383a4b2-b581-4a45-8e8e-491cc5670a2f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AirCraftGlassProductionBVMember_647761df-9df7-4c7e-9a27-afe62511db7c" xlink:href="gntx-20240331.xsd#gntx_AirCraftGlassProductionBVMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_807cd573-a3ed-4527-9ea7-1b9924238b31" xlink:to="loc_gntx_AirCraftGlassProductionBVMember_647761df-9df7-4c7e-9a27-afe62511db7c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_GuardianOpticalTechnologiesMember_12d970f6-6b7b-41c9-b05d-bc65f3b0dfdf" xlink:href="gntx-20240331.xsd#gntx_GuardianOpticalTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_807cd573-a3ed-4527-9ea7-1b9924238b31" xlink:to="loc_gntx_GuardianOpticalTechnologiesMember_12d970f6-6b7b-41c9-b05d-bc65f3b0dfdf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_bddeb0a1-d913-436d-8c45-e0f7af6cd5bb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_7f582e57-ee41-4969-9d35-99a3c6744cf9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_bddeb0a1-d913-436d-8c45-e0f7af6cd5bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_1211ff2c-a863-41b5-b8db-54042c804b67" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_7f582e57-ee41-4969-9d35-99a3c6744cf9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_1211ff2c-a863-41b5-b8db-54042c804b67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_4f62a275-6926-47a4-a5de-83f3d7d8f78f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_7f582e57-ee41-4969-9d35-99a3c6744cf9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_4f62a275-6926-47a4-a5de-83f3d7d8f78f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_3eb02c01-307f-4282-b78c-6a2bf0a426e9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_7f582e57-ee41-4969-9d35-99a3c6744cf9" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_3eb02c01-307f-4282-b78c-6a2bf0a426e9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_a18dcae5-b7b8-4971-bb13-c399f8dc99d5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_7f582e57-ee41-4969-9d35-99a3c6744cf9" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_a18dcae5-b7b8-4971-bb13-c399f8dc99d5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_478ba32b-cf58-4bc5-a3a1-4818dd102d62" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_7f582e57-ee41-4969-9d35-99a3c6744cf9" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_478ba32b-cf58-4bc5-a3a1-4818dd102d62" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_IntangiblePatentsAndAssetsGrossExcludingGoodwill_96aa0a5b-ad61-4b41-aec2-f6bb1a5a1bb8" xlink:href="gntx-20240331.xsd#gntx_IntangiblePatentsAndAssetsGrossExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_7f582e57-ee41-4969-9d35-99a3c6744cf9" xlink:to="loc_gntx_IntangiblePatentsAndAssetsGrossExcludingGoodwill_96aa0a5b-ad61-4b41-aec2-f6bb1a5a1bb8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_FiniteLivedIntangiblePatentsAndAssetsAccumulatedAmortization_149574df-d924-4600-98ca-3a097c5dcb70" xlink:href="gntx-20240331.xsd#gntx_FiniteLivedIntangiblePatentsAndAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_7f582e57-ee41-4969-9d35-99a3c6744cf9" xlink:to="loc_gntx_FiniteLivedIntangiblePatentsAndAssetsAccumulatedAmortization_149574df-d924-4600-98ca-3a097c5dcb70" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_IntangiblePatentsAndAssetsNetExcludingGoodwill_34dfe6dc-05ce-43ff-b279-a2d10e73d97d" xlink:href="gntx-20240331.xsd#gntx_IntangiblePatentsAndAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_7f582e57-ee41-4969-9d35-99a3c6744cf9" xlink:to="loc_gntx_IntangiblePatentsAndAssetsNetExcludingGoodwill_34dfe6dc-05ce-43ff-b279-a2d10e73d97d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_2ca71131-292e-4373-a84e-67caf947bac9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_7f582e57-ee41-4969-9d35-99a3c6744cf9" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_2ca71131-292e-4373-a84e-67caf947bac9" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsNarrativeDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#InvestmentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9acb10af-647e-4f5a-b192-e0eaf2e06c3b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_698eebe5-2e1b-4a02-b884-3014358dc886" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9acb10af-647e-4f5a-b192-e0eaf2e06c3b" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_698eebe5-2e1b-4a02-b884-3014358dc886" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_020fc271-7a79-4814-862a-b8660f46ee31" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_698eebe5-2e1b-4a02-b884-3014358dc886" xlink:to="loc_srt_CounterpartyNameAxis_020fc271-7a79-4814-862a-b8660f46ee31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_020fc271-7a79-4814-862a-b8660f46ee31_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_020fc271-7a79-4814-862a-b8660f46ee31" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_020fc271-7a79-4814-862a-b8660f46ee31_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_98ce9c21-5a19-493f-908a-124c0217c9bf" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_020fc271-7a79-4814-862a-b8660f46ee31" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_98ce9c21-5a19-493f-908a-124c0217c9bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_VOXXInternationalCorporationMember_4b67608a-97f3-4384-9d63-231c0ff22962" xlink:href="gntx-20240331.xsd#gntx_VOXXInternationalCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_98ce9c21-5a19-493f-908a-124c0217c9bf" xlink:to="loc_gntx_VOXXInternationalCorporationMember_4b67608a-97f3-4384-9d63-231c0ff22962" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_6d466446-5679-45e7-a360-6376746ac353" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_698eebe5-2e1b-4a02-b884-3014358dc886" xlink:to="loc_us-gaap_StatementClassOfStockAxis_6d466446-5679-45e7-a360-6376746ac353" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_6d466446-5679-45e7-a360-6376746ac353_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_6d466446-5679-45e7-a360-6376746ac353" xlink:to="loc_us-gaap_ClassOfStockDomain_6d466446-5679-45e7-a360-6376746ac353_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_186cd460-98fe-4d48-8e3b-e8a46a54b137" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_6d466446-5679-45e7-a360-6376746ac353" xlink:to="loc_us-gaap_ClassOfStockDomain_186cd460-98fe-4d48-8e3b-e8a46a54b137" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_2c820ba9-cb9b-43a2-bb07-afc440f8acc9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_186cd460-98fe-4d48-8e3b-e8a46a54b137" xlink:to="loc_us-gaap_CommonClassAMember_2c820ba9-cb9b-43a2-bb07-afc440f8acc9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_51939d5d-4098-4769-9fac-4eafb07616cf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_698eebe5-2e1b-4a02-b884-3014358dc886" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_51939d5d-4098-4769-9fac-4eafb07616cf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_51939d5d-4098-4769-9fac-4eafb07616cf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_51939d5d-4098-4769-9fac-4eafb07616cf" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_51939d5d-4098-4769-9fac-4eafb07616cf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_0a1c3c63-0de7-4656-80e2-3b409d6d1284" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_51939d5d-4098-4769-9fac-4eafb07616cf" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_0a1c3c63-0de7-4656-80e2-3b409d6d1284" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_LongTermInvestmentsMember_b8c77020-3cfd-411b-86b2-66b17da3915f" xlink:href="gntx-20240331.xsd#gntx_LongTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_0a1c3c63-0de7-4656-80e2-3b409d6d1284" xlink:to="loc_gntx_LongTermInvestmentsMember_b8c77020-3cfd-411b-86b2-66b17da3915f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_9417f4ed-8c67-4539-a42f-973c5b6ae2cd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_0a1c3c63-0de7-4656-80e2-3b409d6d1284" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_9417f4ed-8c67-4539-a42f-973c5b6ae2cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_StockPurchaseAgreementNumberOfSharesAcquired_36b8843b-ef26-4e59-b5e7-1b042af2c702" xlink:href="gntx-20240331.xsd#gntx_StockPurchaseAgreementNumberOfSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9acb10af-647e-4f5a-b192-e0eaf2e06c3b" xlink:to="loc_gntx_StockPurchaseAgreementNumberOfSharesAcquired_36b8843b-ef26-4e59-b5e7-1b042af2c702" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_StockPurchaseAgreementSharesAcquiredNumberOfTranches_71fe35a1-39a6-47c4-9e7b-3432a9535de5" xlink:href="gntx-20240331.xsd#gntx_StockPurchaseAgreementSharesAcquiredNumberOfTranches"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9acb10af-647e-4f5a-b192-e0eaf2e06c3b" xlink:to="loc_gntx_StockPurchaseAgreementSharesAcquiredNumberOfTranches_71fe35a1-39a6-47c4-9e7b-3432a9535de5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_StockPurchaseAgreementSharePrice_0d75ce78-df41-4fc0-9743-473d89caec83" xlink:href="gntx-20240331.xsd#gntx_StockPurchaseAgreementSharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9acb10af-647e-4f5a-b192-e0eaf2e06c3b" xlink:to="loc_gntx_StockPurchaseAgreementSharePrice_0d75ce78-df41-4fc0-9743-473d89caec83" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_26711bf4-f48c-445b-9a16-5e3b7bcdd242" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9acb10af-647e-4f5a-b192-e0eaf2e06c3b" xlink:to="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_26711bf4-f48c-445b-9a16-5e3b7bcdd242" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9586de1b-aa7d-4198-90c2-99c9a2dc4d94" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_774940a9-586e-4a7f-aee3-3c46e0e73500" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9586de1b-aa7d-4198-90c2-99c9a2dc4d94" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_774940a9-586e-4a7f-aee3-3c46e0e73500" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c0f9cc05-72ea-4aad-8c56-0d61d3392447" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_774940a9-586e-4a7f-aee3-3c46e0e73500" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c0f9cc05-72ea-4aad-8c56-0d61d3392447" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c0f9cc05-72ea-4aad-8c56-0d61d3392447_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c0f9cc05-72ea-4aad-8c56-0d61d3392447" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c0f9cc05-72ea-4aad-8c56-0d61d3392447_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b1206715-0bf5-42bd-aa71-80d3b3743f9c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_c0f9cc05-72ea-4aad-8c56-0d61d3392447" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b1206715-0bf5-42bd-aa71-80d3b3743f9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_3eab6aba-4a40-42df-ac7d-7e640e68ea2f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b1206715-0bf5-42bd-aa71-80d3b3743f9c" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_3eab6aba-4a40-42df-ac7d-7e640e68ea2f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_6c972d15-4d2a-478d-a2d8-e6dde7d444d6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b1206715-0bf5-42bd-aa71-80d3b3743f9c" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_6c972d15-4d2a-478d-a2d8-e6dde7d444d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_c1e6da9d-f0d6-4cba-8c53-5841ea54a377" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b1206715-0bf5-42bd-aa71-80d3b3743f9c" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_c1e6da9d-f0d6-4cba-8c53-5841ea54a377" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_4fbf2444-5aed-4e90-b4eb-ed8e3e4c98f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_774940a9-586e-4a7f-aee3-3c46e0e73500" xlink:to="loc_us-gaap_InvestmentTypeAxis_4fbf2444-5aed-4e90-b4eb-ed8e3e4c98f5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_4fbf2444-5aed-4e90-b4eb-ed8e3e4c98f5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_4fbf2444-5aed-4e90-b4eb-ed8e3e4c98f5" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_4fbf2444-5aed-4e90-b4eb-ed8e3e4c98f5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_775a51d6-8dc7-42b7-9704-05e627f55be4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_4fbf2444-5aed-4e90-b4eb-ed8e3e4c98f5" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_775a51d6-8dc7-42b7-9704-05e627f55be4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_faeeceb8-5f0a-45ca-bad1-29690d0c08f6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_775a51d6-8dc7-42b7-9704-05e627f55be4" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_faeeceb8-5f0a-45ca-bad1-29690d0c08f6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermInvestmentsMember_dba49716-e675-4927-9b68-0d1de1c9df3e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLongTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_775a51d6-8dc7-42b7-9704-05e627f55be4" xlink:to="loc_us-gaap_OtherLongTermInvestmentsMember_dba49716-e675-4927-9b68-0d1de1c9df3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_8a3cbb2f-4c07-43f8-9f3c-4abec3864f67" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_774940a9-586e-4a7f-aee3-3c46e0e73500" xlink:to="loc_us-gaap_FinancialInstrumentAxis_8a3cbb2f-4c07-43f8-9f3c-4abec3864f67" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8a3cbb2f-4c07-43f8-9f3c-4abec3864f67_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_8a3cbb2f-4c07-43f8-9f3c-4abec3864f67" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8a3cbb2f-4c07-43f8-9f3c-4abec3864f67_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9837a93e-fcda-4532-89b5-b1ef116138f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_8a3cbb2f-4c07-43f8-9f3c-4abec3864f67" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9837a93e-fcda-4532-89b5-b1ef116138f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_e7c088f6-907d-4462-b7e9-a121c56bc6cb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9837a93e-fcda-4532-89b5-b1ef116138f5" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_e7c088f6-907d-4462-b7e9-a121c56bc6cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_db4eab40-1b45-4dd5-9b73-53dd208fcfc2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9837a93e-fcda-4532-89b5-b1ef116138f5" xlink:to="loc_us-gaap_CertificatesOfDepositMember_db4eab40-1b45-4dd5-9b73-53dd208fcfc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_eafb2c22-36a5-40a3-bfa8-b7ea13ccb23a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateBondSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9837a93e-fcda-4532-89b5-b1ef116138f5" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_eafb2c22-36a5-40a3-bfa8-b7ea13ccb23a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_308f9e4f-0b55-4070-a840-726639bd8d01" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9837a93e-fcda-4532-89b5-b1ef116138f5" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_308f9e4f-0b55-4070-a840-726639bd8d01" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MunicipalBondsMember_e9dac8a0-0a0a-4fbf-b2f7-8fc71d166033" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MunicipalBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9837a93e-fcda-4532-89b5-b1ef116138f5" xlink:to="loc_us-gaap_MunicipalBondsMember_e9dac8a0-0a0a-4fbf-b2f7-8fc71d166033" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_a4890885-e20b-4902-a227-0f5dd1493684" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9837a93e-fcda-4532-89b5-b1ef116138f5" xlink:to="loc_us-gaap_OtherDebtSecuritiesMember_a4890885-e20b-4902-a227-0f5dd1493684" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_d578a289-b2e6-44a3-9bbd-8309e7e73fa3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9837a93e-fcda-4532-89b5-b1ef116138f5" xlink:to="loc_us-gaap_CommonStockMember_d578a289-b2e6-44a3-9bbd-8309e7e73fa3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_fe54682e-1a82-4f20-be87-82a09bba51d3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9586de1b-aa7d-4198-90c2-99c9a2dc4d94" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_fe54682e-1a82-4f20-be87-82a09bba51d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_5f2f00a2-b93f-43c0-a1f4-82f5b62e2dec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9586de1b-aa7d-4198-90c2-99c9a2dc4d94" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_5f2f00a2-b93f-43c0-a1f4-82f5b62e2dec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_f3f7f379-6161-4e25-b30e-5c23caafeb25" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9586de1b-aa7d-4198-90c2-99c9a2dc4d94" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_f3f7f379-6161-4e25-b30e-5c23caafeb25" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_e0423103-f302-4a8a-a1cd-ca79b20dca7c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_3d1f3fa4-a945-4dbd-9092-62571fd51b39" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_e0423103-f302-4a8a-a1cd-ca79b20dca7c" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_3d1f3fa4-a945-4dbd-9092-62571fd51b39" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_InvestmentLengthAxis_2641da7d-ff09-4de6-8c42-3f20f53d0459" xlink:href="gntx-20240331.xsd#gntx_InvestmentLengthAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_3d1f3fa4-a945-4dbd-9092-62571fd51b39" xlink:to="loc_gntx_InvestmentLengthAxis_2641da7d-ff09-4de6-8c42-3f20f53d0459" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_InvestmentLengthDomain_2641da7d-ff09-4de6-8c42-3f20f53d0459_default" xlink:href="gntx-20240331.xsd#gntx_InvestmentLengthDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_gntx_InvestmentLengthAxis_2641da7d-ff09-4de6-8c42-3f20f53d0459" xlink:to="loc_gntx_InvestmentLengthDomain_2641da7d-ff09-4de6-8c42-3f20f53d0459_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_InvestmentLengthDomain_c71e141f-96f9-41bf-bcab-d62ba894a6bb" xlink:href="gntx-20240331.xsd#gntx_InvestmentLengthDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_gntx_InvestmentLengthAxis_2641da7d-ff09-4de6-8c42-3f20f53d0459" xlink:to="loc_gntx_InvestmentLengthDomain_c71e141f-96f9-41bf-bcab-d62ba894a6bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_7558c0c0-29b7-4db0-a18e-efe95c06691a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_InvestmentLengthDomain_c71e141f-96f9-41bf-bcab-d62ba894a6bb" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_7558c0c0-29b7-4db0-a18e-efe95c06691a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermInvestmentsMember_1f92fd31-3c1c-45f8-83e2-77dcdf8522f6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLongTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_InvestmentLengthDomain_c71e141f-96f9-41bf-bcab-d62ba894a6bb" xlink:to="loc_us-gaap_OtherLongTermInvestmentsMember_1f92fd31-3c1c-45f8-83e2-77dcdf8522f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_0c62f523-27a5-423a-85b3-afa880b46618" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_3d1f3fa4-a945-4dbd-9092-62571fd51b39" xlink:to="loc_us-gaap_FinancialInstrumentAxis_0c62f523-27a5-423a-85b3-afa880b46618" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_0c62f523-27a5-423a-85b3-afa880b46618_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_0c62f523-27a5-423a-85b3-afa880b46618" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_0c62f523-27a5-423a-85b3-afa880b46618_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_edbbea4b-7a5f-4229-a9b9-7de83b8a5ae4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_0c62f523-27a5-423a-85b3-afa880b46618" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_edbbea4b-7a5f-4229-a9b9-7de83b8a5ae4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_55e33efe-0c9c-4534-9614-b0ad78a9ce99" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_edbbea4b-7a5f-4229-a9b9-7de83b8a5ae4" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_55e33efe-0c9c-4534-9614-b0ad78a9ce99" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_bd63f9e8-4971-4a08-8982-fb398460f458" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_edbbea4b-7a5f-4229-a9b9-7de83b8a5ae4" xlink:to="loc_us-gaap_CertificatesOfDepositMember_bd63f9e8-4971-4a08-8982-fb398460f458" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_b60ab8fd-4704-4251-990f-9f300c4a1dc0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CorporateBondSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_edbbea4b-7a5f-4229-a9b9-7de83b8a5ae4" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_b60ab8fd-4704-4251-990f-9f300c4a1dc0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_6ed349c0-a9f3-4e5d-a6e4-0ce290f2a170" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_edbbea4b-7a5f-4229-a9b9-7de83b8a5ae4" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_6ed349c0-a9f3-4e5d-a6e4-0ce290f2a170" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MunicipalBondsMember_d44a12bc-d5df-4d84-92e2-f01f7c36e289" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MunicipalBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_edbbea4b-7a5f-4229-a9b9-7de83b8a5ae4" xlink:to="loc_us-gaap_MunicipalBondsMember_d44a12bc-d5df-4d84-92e2-f01f7c36e289" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_9cd74b0a-c0ff-475e-b6a6-829894e61ecd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_edbbea4b-7a5f-4229-a9b9-7de83b8a5ae4" xlink:to="loc_us-gaap_OtherDebtSecuritiesMember_9cd74b0a-c0ff-475e-b6a6-829894e61ecd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_f8abbfa1-05c2-4aa4-a352-7aeba5e16142" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_edbbea4b-7a5f-4229-a9b9-7de83b8a5ae4" xlink:to="loc_us-gaap_CommonStockMember_f8abbfa1-05c2-4aa4-a352-7aeba5e16142" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_dcfbd018-cb97-42b5-a74e-3de79d58511e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_e0423103-f302-4a8a-a1cd-ca79b20dca7c" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_dcfbd018-cb97-42b5-a74e-3de79d58511e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_0b7a5e1b-5038-4e51-b53c-313c0f5d825d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_e0423103-f302-4a8a-a1cd-ca79b20dca7c" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_0b7a5e1b-5038-4e51-b53c-313c0f5d825d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_a93aba92-875a-4177-9451-2aa145f6ac30" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_e0423103-f302-4a8a-a1cd-ca79b20dca7c" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_a93aba92-875a-4177-9451-2aa145f6ac30" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_0f37c1cb-2f9a-42b4-94ad-5fcf12f372b0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_e0423103-f302-4a8a-a1cd-ca79b20dca7c" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_0f37c1cb-2f9a-42b4-94ad-5fcf12f372b0" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsScheduleofInvestmentsClassifiedbyContractualMaturityDateDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#InvestmentsScheduleofInvestmentsClassifiedbyContractualMaturityDateDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsScheduleofInvestmentsClassifiedbyContractualMaturityDateDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_6aa707a6-828d-4fff-b492-5e558a055022" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_e26d3030-1ce1-4a21-ae83-4429d5ebfb97" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_6aa707a6-828d-4fff-b492-5e558a055022" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_e26d3030-1ce1-4a21-ae83-4429d5ebfb97" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_1218e149-3c95-450d-a10e-a2101cfc3f92" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_e26d3030-1ce1-4a21-ae83-4429d5ebfb97" xlink:to="loc_us-gaap_FinancialInstrumentAxis_1218e149-3c95-450d-a10e-a2101cfc3f92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1218e149-3c95-450d-a10e-a2101cfc3f92_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_1218e149-3c95-450d-a10e-a2101cfc3f92" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1218e149-3c95-450d-a10e-a2101cfc3f92_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9165a4f7-3bbf-4b7f-b8d8-7e19402e1125" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_1218e149-3c95-450d-a10e-a2101cfc3f92" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9165a4f7-3bbf-4b7f-b8d8-7e19402e1125" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedIncomeSecuritiesMember_9306c9c6-1540-4a7e-aece-90211f6e3bae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FixedIncomeSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_9165a4f7-3bbf-4b7f-b8d8-7e19402e1125" xlink:to="loc_us-gaap_FixedIncomeSecuritiesMember_9306c9c6-1540-4a7e-aece-90211f6e3bae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_7a0c70f1-f79f-48e9-84cc-c41654f52a5a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_6aa707a6-828d-4fff-b492-5e558a055022" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_7a0c70f1-f79f-48e9-84cc-c41654f52a5a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_1e6e5d45-63d9-46a0-993e-d69c1c96f8cc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_6aa707a6-828d-4fff-b492-5e558a055022" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_1e6e5d45-63d9-46a0-993e-d69c1c96f8cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterFiveYearsFairValue_a060c0d2-4c6b-4274-9ca8-a6b0e99a7c1b" xlink:href="gntx-20240331.xsd#gntx_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_6aa707a6-828d-4fff-b492-5e558a055022" xlink:to="loc_gntx_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterFiveYearsFairValue_a060c0d2-4c6b-4274-9ca8-a6b0e99a7c1b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_62446d0b-3e05-4221-80d4-548a5d76703b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_6aa707a6-828d-4fff-b492-5e558a055022" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_62446d0b-3e05-4221-80d4-548a5d76703b" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlansNarrativeDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#StockBasedCompensationPlansNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlansNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_14444cfd-87c5-4564-8c7a-a593737850e7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_14444cfd-87c5-4564-8c7a-a593737850e7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_ec568e38-5d31-4b4c-8735-8e7cf9f346f0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_14444cfd-87c5-4564-8c7a-a593737850e7" xlink:to="loc_us-gaap_AwardTypeAxis_ec568e38-5d31-4b4c-8735-8e7cf9f346f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ec568e38-5d31-4b4c-8735-8e7cf9f346f0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_ec568e38-5d31-4b4c-8735-8e7cf9f346f0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_ec568e38-5d31-4b4c-8735-8e7cf9f346f0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_89abc0a5-936e-4a73-b7e1-27446341f1d8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_ec568e38-5d31-4b4c-8735-8e7cf9f346f0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_89abc0a5-936e-4a73-b7e1-27446341f1d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockCompensationPlanMember_dd4e1ce2-d0ea-45df-9c49-b0c7ebbdfd36" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockCompensationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_89abc0a5-936e-4a73-b7e1-27446341f1d8" xlink:to="loc_us-gaap_StockCompensationPlanMember_dd4e1ce2-d0ea-45df-9c49-b0c7ebbdfd36" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_0115d6b9-fff4-465e-98de-4d69286202d4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_89abc0a5-936e-4a73-b7e1-27446341f1d8" xlink:to="loc_us-gaap_PerformanceSharesMember_0115d6b9-fff4-465e-98de-4d69286202d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_PerformanceShareAwardsMember_efe9e844-24c9-40b9-b8b3-7ec98d70cb23" xlink:href="gntx-20240331.xsd#gntx_PerformanceShareAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_89abc0a5-936e-4a73-b7e1-27446341f1d8" xlink:to="loc_gntx_PerformanceShareAwardsMember_efe9e844-24c9-40b9-b8b3-7ec98d70cb23" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_963f32e2-ecc9-4bba-9292-439bf664b0df" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_14444cfd-87c5-4564-8c7a-a593737850e7" xlink:to="loc_us-gaap_PlanNameAxis_963f32e2-ecc9-4bba-9292-439bf664b0df" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_963f32e2-ecc9-4bba-9292-439bf664b0df_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_963f32e2-ecc9-4bba-9292-439bf664b0df" xlink:to="loc_us-gaap_PlanNameDomain_963f32e2-ecc9-4bba-9292-439bf664b0df_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_7c3c46fc-da6e-4e78-8344-27217ae3c3f1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_963f32e2-ecc9-4bba-9292-439bf664b0df" xlink:to="loc_us-gaap_PlanNameDomain_7c3c46fc-da6e-4e78-8344-27217ae3c3f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OmnibusIncentivePlanMember_11044e39-2e00-4e96-b270-d27a16ede72a" xlink:href="gntx-20240331.xsd#gntx_OmnibusIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_7c3c46fc-da6e-4e78-8344-27217ae3c3f1" xlink:to="loc_gntx_OmnibusIncentivePlanMember_11044e39-2e00-4e96-b270-d27a16ede72a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_EmployeeStockOptionPlanMember_76202db8-a50f-47bb-ad17-778c1d0c6c6f" xlink:href="gntx-20240331.xsd#gntx_EmployeeStockOptionPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_7c3c46fc-da6e-4e78-8344-27217ae3c3f1" xlink:to="loc_gntx_EmployeeStockOptionPlanMember_76202db8-a50f-47bb-ad17-778c1d0c6c6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_RestrictedStockPlanMember_556a688a-efa3-4241-b336-7fc076e1c0f5" xlink:href="gntx-20240331.xsd#gntx_RestrictedStockPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_7c3c46fc-da6e-4e78-8344-27217ae3c3f1" xlink:to="loc_gntx_RestrictedStockPlanMember_556a688a-efa3-4241-b336-7fc076e1c0f5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_GentexCorporationEmployeeStockPurchasePlanMember_e9461ed0-3a7a-4219-a8e3-a8489117ac46" xlink:href="gntx-20240331.xsd#gntx_GentexCorporationEmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_7c3c46fc-da6e-4e78-8344-27217ae3c3f1" xlink:to="loc_gntx_GentexCorporationEmployeeStockPurchasePlanMember_e9461ed0-3a7a-4219-a8e3-a8489117ac46" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_eecc27a9-a241-410d-aeed-b93aaf60954e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_14444cfd-87c5-4564-8c7a-a593737850e7" xlink:to="loc_srt_RangeAxis_eecc27a9-a241-410d-aeed-b93aaf60954e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_eecc27a9-a241-410d-aeed-b93aaf60954e_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_eecc27a9-a241-410d-aeed-b93aaf60954e" xlink:to="loc_srt_RangeMember_eecc27a9-a241-410d-aeed-b93aaf60954e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_b034bbd5-46e1-4953-9751-1a7f9f19a4d8" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_eecc27a9-a241-410d-aeed-b93aaf60954e" xlink:to="loc_srt_RangeMember_b034bbd5-46e1-4953-9751-1a7f9f19a4d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_72108332-5e9d-4a93-8061-4295cca6d666" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_b034bbd5-46e1-4953-9751-1a7f9f19a4d8" xlink:to="loc_srt_MinimumMember_72108332-5e9d-4a93-8061-4295cca6d666" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_3a334148-4431-4aa4-9153-f1a9615f5513" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_b034bbd5-46e1-4953-9751-1a7f9f19a4d8" xlink:to="loc_srt_MaximumMember_3a334148-4431-4aa4-9153-f1a9615f5513" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_6ad77374-a9bd-44fc-a3fe-645dd1d843e8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_14444cfd-87c5-4564-8c7a-a593737850e7" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_6ad77374-a9bd-44fc-a3fe-645dd1d843e8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_6ad77374-a9bd-44fc-a3fe-645dd1d843e8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_6ad77374-a9bd-44fc-a3fe-645dd1d843e8" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_6ad77374-a9bd-44fc-a3fe-645dd1d843e8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_16c2041a-78a0-49f0-abc7-c649b621884d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_6ad77374-a9bd-44fc-a3fe-645dd1d843e8" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_16c2041a-78a0-49f0-abc7-c649b621884d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_0745f8fa-9410-4346-bc2d-766c80184fc5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_16c2041a-78a0-49f0-abc7-c649b621884d" xlink:to="loc_us-gaap_EmployeeStockMember_0745f8fa-9410-4346-bc2d-766c80184fc5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfPlans_792bc3f7-24f5-475d-b22d-3bedb566a8bd" xlink:href="gntx-20240331.xsd#gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfPlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfPlans_792bc3f7-24f5-475d-b22d-3bedb566a8bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_86a6cc3e-8453-43fa-829e-81e0ad003664" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_86a6cc3e-8453-43fa-829e-81e0ad003664" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod_3d0fddcf-b399-4945-b202-820aba96e5e5" xlink:href="gntx-20240331.xsd#gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod_3d0fddcf-b399-4945-b202-820aba96e5e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_5473e54b-a98f-4f77-bb17-50f3b4178e0d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_5473e54b-a98f-4f77-bb17-50f3b4178e0d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_8602803a-8fee-4322-ade8-3ad9bbd075dd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_8602803a-8fee-4322-ade8-3ad9bbd075dd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_0e18549f-61b9-4385-b0c5-2826843ac42f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_0e18549f-61b9-4385-b0c5-2826843ac42f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_0542698d-d0a5-48f4-a506-2456bbd79c23" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_0542698d-d0a5-48f4-a506-2456bbd79c23" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_795472fd-d979-4e52-a43b-b6e8ce76c06a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_795472fd-d979-4e52-a43b-b6e8ce76c06a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedPaymentArrangementRestrictedPeriod_b349169b-f4da-45b4-af1c-07502424b81e" xlink:href="gntx-20240331.xsd#gntx_ShareBasedPaymentArrangementRestrictedPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:to="loc_gntx_ShareBasedPaymentArrangementRestrictedPeriod_b349169b-f4da-45b4-af1c-07502424b81e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockExpense_e3be1729-98ad-49ec-87b2-f71bc6eda087" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:to="loc_us-gaap_RestrictedStockExpense_e3be1729-98ad-49ec-87b2-f71bc6eda087" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_ab1f205e-def1-4644-a77a-fe406fe26ef9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_ab1f205e-def1-4644-a77a-fe406fe26ef9" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense_af2d1676-fd63-4cb7-b475-1cacc15718ec" xlink:href="gntx-20240331.xsd#gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f4e0ca88-caeb-4c61-abe6-7f60df43efbc" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense_af2d1676-fd63-4cb7-b475-1cacc15718ec" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlansScheduleofSharesIssuedNetofSharesCanceledExpiredDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#StockBasedCompensationPlansScheduleofSharesIssuedNetofSharesCanceledExpiredDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlansScheduleofSharesIssuedNetofSharesCanceledExpiredDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7fd22560-7b25-43fb-b939-3873464571b6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_dd6df0e2-4cc6-4f9b-a34a-3346e9ccfbf2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7fd22560-7b25-43fb-b939-3873464571b6" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_dd6df0e2-4cc6-4f9b-a34a-3346e9ccfbf2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_482b0bb3-17fe-4c34-8a0e-9f27b82e7067" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_dd6df0e2-4cc6-4f9b-a34a-3346e9ccfbf2" xlink:to="loc_us-gaap_PlanNameAxis_482b0bb3-17fe-4c34-8a0e-9f27b82e7067" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_482b0bb3-17fe-4c34-8a0e-9f27b82e7067_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_482b0bb3-17fe-4c34-8a0e-9f27b82e7067" xlink:to="loc_us-gaap_PlanNameDomain_482b0bb3-17fe-4c34-8a0e-9f27b82e7067_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_c0f571ab-3728-44bb-bcd4-491baed5c143" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_482b0bb3-17fe-4c34-8a0e-9f27b82e7067" xlink:to="loc_us-gaap_PlanNameDomain_c0f571ab-3728-44bb-bcd4-491baed5c143" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OmnibusIncentivePlanMember_97ac3866-efa0-4683-a0c0-5a16300cbf4e" xlink:href="gntx-20240331.xsd#gntx_OmnibusIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_c0f571ab-3728-44bb-bcd4-491baed5c143" xlink:to="loc_gntx_OmnibusIncentivePlanMember_97ac3866-efa0-4683-a0c0-5a16300cbf4e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_5b089527-ce6b-4d23-acf5-92f591ed306a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_dd6df0e2-4cc6-4f9b-a34a-3346e9ccfbf2" xlink:to="loc_us-gaap_AwardTypeAxis_5b089527-ce6b-4d23-acf5-92f591ed306a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5b089527-ce6b-4d23-acf5-92f591ed306a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_5b089527-ce6b-4d23-acf5-92f591ed306a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5b089527-ce6b-4d23-acf5-92f591ed306a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8f4bcd4d-7769-44b2-83ca-b88367179807" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_5b089527-ce6b-4d23-acf5-92f591ed306a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8f4bcd4d-7769-44b2-83ca-b88367179807" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_NonQualifiedStockOptionMember_a3d197a0-747b-4999-ba84-a1a0f843c6c5" xlink:href="gntx-20240331.xsd#gntx_NonQualifiedStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8f4bcd4d-7769-44b2-83ca-b88367179807" xlink:to="loc_gntx_NonQualifiedStockOptionMember_a3d197a0-747b-4999-ba84-a1a0f843c6c5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_4d6d56d3-5d86-4fcc-b9e3-a4bbe4b7d8d8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8f4bcd4d-7769-44b2-83ca-b88367179807" xlink:to="loc_us-gaap_RestrictedStockMember_4d6d56d3-5d86-4fcc-b9e3-a4bbe4b7d8d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_e10131cd-3c7f-4e22-8e20-44de1a104b86" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8f4bcd4d-7769-44b2-83ca-b88367179807" xlink:to="loc_us-gaap_PerformanceSharesMember_e10131cd-3c7f-4e22-8e20-44de1a104b86" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_911cc75b-d83f-4b9d-901b-64546e21c55f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7fd22560-7b25-43fb-b939-3873464571b6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_911cc75b-d83f-4b9d-901b-64546e21c55f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_756b5a77-67b3-44e2-ac84-c0a055ee8708" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7fd22560-7b25-43fb-b939-3873464571b6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_756b5a77-67b3-44e2-ac84-c0a055ee8708" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod_610f1832-505a-4110-8991-d99e71f2d67f" xlink:href="gntx-20240331.xsd#gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7fd22560-7b25-43fb-b939-3873464571b6" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod_610f1832-505a-4110-8991-d99e71f2d67f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsConversionRate_0a46721c-f08b-4db5-ad8e-fd5527bedcb3" xlink:href="gntx-20240331.xsd#gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsConversionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7fd22560-7b25-43fb-b939-3873464571b6" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsConversionRate_0a46721c-f08b-4db5-ad8e-fd5527bedcb3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentConversionRate_12182df0-53c2-4d06-965f-b875bb0ffd4f" xlink:href="gntx-20240331.xsd#gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentConversionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7fd22560-7b25-43fb-b939-3873464571b6" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentConversionRate_12182df0-53c2-4d06-965f-b875bb0ffd4f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_c8ae0869-11a8-4191-ae67-465e22bfe234" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7fd22560-7b25-43fb-b939-3873464571b6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_c8ae0869-11a8-4191-ae67-465e22bfe234" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncomeLossScheduleofAOCIRollforwardDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#ComprehensiveIncomeLossScheduleofAOCIRollforwardDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncomeLossScheduleofAOCIRollforwardDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_11d855a7-2fee-4537-bbba-50f539cd5eb6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_066e7e3e-1b96-4e0d-b29e-67774ec70e46" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_11d855a7-2fee-4537-bbba-50f539cd5eb6" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_066e7e3e-1b96-4e0d-b29e-67774ec70e46" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_0651cf80-c315-427c-a3dd-448acd554859" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_066e7e3e-1b96-4e0d-b29e-67774ec70e46" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_0651cf80-c315-427c-a3dd-448acd554859" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_0651cf80-c315-427c-a3dd-448acd554859_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_0651cf80-c315-427c-a3dd-448acd554859" xlink:to="loc_us-gaap_EquityComponentDomain_0651cf80-c315-427c-a3dd-448acd554859_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_6b541b7f-fdc3-49ed-8d79-c80c0b007a62" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_0651cf80-c315-427c-a3dd-448acd554859" xlink:to="loc_us-gaap_EquityComponentDomain_6b541b7f-fdc3-49ed-8d79-c80c0b007a62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_75d783bc-bf6c-40ed-aa36-91e9729c530f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_6b541b7f-fdc3-49ed-8d79-c80c0b007a62" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_75d783bc-bf6c-40ed-aa36-91e9729c530f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_7698df12-1dd8-44e4-b84f-c4f91a80fb0e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_75d783bc-bf6c-40ed-aa36-91e9729c530f" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_7698df12-1dd8-44e4-b84f-c4f91a80fb0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_2d4b7f9c-2415-4d44-b23b-dd2f42fad702" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_75d783bc-bf6c-40ed-aa36-91e9729c530f" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_2d4b7f9c-2415-4d44-b23b-dd2f42fad702" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_7e02d041-feb0-4f91-a0a0-d69fb9e16e91" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_11d855a7-2fee-4537-bbba-50f539cd5eb6" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_7e02d041-feb0-4f91-a0a0-d69fb9e16e91" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_1b3ccb25-7f0d-46be-8d40-81f40d630ab8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_7e02d041-feb0-4f91-a0a0-d69fb9e16e91" xlink:to="loc_us-gaap_StockholdersEquity_1b3ccb25-7f0d-46be-8d40-81f40d630ab8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_ca7a0ec5-a911-4a54-adf2-2b5ad8ddd7db" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_7e02d041-feb0-4f91-a0a0-d69fb9e16e91" xlink:to="loc_us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent_ca7a0ec5-a911-4a54-adf2-2b5ad8ddd7db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_378132b8-86c0-4d5b-b828-dbf9313776cf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_7e02d041-feb0-4f91-a0a0-d69fb9e16e91" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent_378132b8-86c0-4d5b-b828-dbf9313776cf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_7324bfcb-781a-4354-bab1-4908b7a0acf0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_7e02d041-feb0-4f91-a0a0-d69fb9e16e91" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_7324bfcb-781a-4354-bab1-4908b7a0acf0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_e77c4ebb-f81d-47aa-a4e4-e30e579533c4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncomeLossScheduleofReclassificationsOutofAccumulatedOtherComprehensiveLossDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#ComprehensiveIncomeLossScheduleofReclassificationsOutofAccumulatedOtherComprehensiveLossDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncomeLossScheduleofReclassificationsOutofAccumulatedOtherComprehensiveLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_f99a1234-4a8b-4985-aae5-ae46183f3e4d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_205cd093-3815-4c31-ae1f-03ad598b5ad4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_f99a1234-4a8b-4985-aae5-ae46183f3e4d" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_205cd093-3815-4c31-ae1f-03ad598b5ad4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_38c722ae-a89a-4e8b-876c-bafe00363a15" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_205cd093-3815-4c31-ae1f-03ad598b5ad4" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_38c722ae-a89a-4e8b-876c-bafe00363a15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_38c722ae-a89a-4e8b-876c-bafe00363a15_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_38c722ae-a89a-4e8b-876c-bafe00363a15" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_38c722ae-a89a-4e8b-876c-bafe00363a15_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_cc0e778e-f86d-42df-b003-1a9dba162f3c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_38c722ae-a89a-4e8b-876c-bafe00363a15" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_cc0e778e-f86d-42df-b003-1a9dba162f3c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_eabf1e0b-42dd-44e9-b9eb-28408fb9e3f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_cc0e778e-f86d-42df-b003-1a9dba162f3c" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_eabf1e0b-42dd-44e9-b9eb-28408fb9e3f5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_ef5f7a20-2fb2-42bc-b139-97d797bcdf3d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_205cd093-3815-4c31-ae1f-03ad598b5ad4" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_ef5f7a20-2fb2-42bc-b139-97d797bcdf3d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_ef5f7a20-2fb2-42bc-b139-97d797bcdf3d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_ef5f7a20-2fb2-42bc-b139-97d797bcdf3d" xlink:to="loc_us-gaap_EquityComponentDomain_ef5f7a20-2fb2-42bc-b139-97d797bcdf3d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_61743041-2014-4112-a3f3-4c3ec294628d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_ef5f7a20-2fb2-42bc-b139-97d797bcdf3d" xlink:to="loc_us-gaap_EquityComponentDomain_61743041-2014-4112-a3f3-4c3ec294628d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_ec0445b7-5098-45a4-9d03-535bae7ab7c0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_61743041-2014-4112-a3f3-4c3ec294628d" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_ec0445b7-5098-45a4-9d03-535bae7ab7c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_989b9841-45b0-4192-bf7a-2d689f011a0f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_f99a1234-4a8b-4985-aae5-ae46183f3e4d" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_989b9841-45b0-4192-bf7a-2d689f011a0f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_92568e01-46a6-4ac2-bd26-8f193bcbee99" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_f99a1234-4a8b-4985-aae5-ae46183f3e4d" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_92568e01-46a6-4ac2-bd26-8f193bcbee99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_4a64c0d2-3aae-414e-affd-0027d410ac41" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_f99a1234-4a8b-4985-aae5-ae46183f3e4d" xlink:to="loc_us-gaap_NetIncomeLoss_4a64c0d2-3aae-414e-affd-0027d410ac41" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/DebtandFinancingArrangementsDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#DebtandFinancingArrangementsDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/DebtandFinancingArrangementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_e7a34e1c-a9de-4e36-ad64-0ad6e418823f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_d793457d-23a8-4fe0-925d-18a69307ddba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e7a34e1c-a9de-4e36-ad64-0ad6e418823f" xlink:to="loc_us-gaap_DebtInstrumentTable_d793457d-23a8-4fe0-925d-18a69307ddba" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_65776955-787e-4692-87c6-bd727330caf6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_d793457d-23a8-4fe0-925d-18a69307ddba" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_65776955-787e-4692-87c6-bd727330caf6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_65776955-787e-4692-87c6-bd727330caf6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_65776955-787e-4692-87c6-bd727330caf6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_65776955-787e-4692-87c6-bd727330caf6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_402df6ad-1797-43c3-aaf5-e1067d159fc8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_65776955-787e-4692-87c6-bd727330caf6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_402df6ad-1797-43c3-aaf5-e1067d159fc8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_0438c0c4-6aa0-4327-9ed6-e0328b405645" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_402df6ad-1797-43c3-aaf5-e1067d159fc8" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_0438c0c4-6aa0-4327-9ed6-e0328b405645" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_6e8182b8-3a7a-45a3-908e-21d2983c96ed" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_402df6ad-1797-43c3-aaf5-e1067d159fc8" xlink:to="loc_us-gaap_LetterOfCreditMember_6e8182b8-3a7a-45a3-908e-21d2983c96ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_SwingLoansMember_5791e41a-51b3-4a48-a196-b151fe4e5e9a" xlink:href="gntx-20240331.xsd#gntx_SwingLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_402df6ad-1797-43c3-aaf5-e1067d159fc8" xlink:to="loc_gntx_SwingLoansMember_5791e41a-51b3-4a48-a196-b151fe4e5e9a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_54e5cb3c-76c4-4e86-a81e-d755bb2e2458" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e7a34e1c-a9de-4e36-ad64-0ad6e418823f" xlink:to="loc_us-gaap_DebtInstrumentTerm_54e5cb3c-76c4-4e86-a81e-d755bb2e2458" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_4f40951b-cef2-4cc4-a177-bb592f0575de" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e7a34e1c-a9de-4e36-ad64-0ad6e418823f" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_4f40951b-cef2-4cc4-a177-bb592f0575de" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount_88a08f7c-769b-4b34-9f2a-23f430f236c9" xlink:href="gntx-20240331.xsd#gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e7a34e1c-a9de-4e36-ad64-0ad6e418823f" xlink:to="loc_gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount_88a08f7c-769b-4b34-9f2a-23f430f236c9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_c67df0da-fe2c-4adb-b153-707bb9b80fee" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e7a34e1c-a9de-4e36-ad64-0ad6e418823f" xlink:to="loc_us-gaap_LongTermDebt_c67df0da-fe2c-4adb-b153-707bb9b80fee" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/SegmentReportingNarrativeDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#SegmentReportingNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/SegmentReportingNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_fe9e5b14-4457-4fbf-accf-a880114a97ba" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a1afb81e-2df1-4801-bec1-c783f1bab69a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_fe9e5b14-4457-4fbf-accf-a880114a97ba" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a1afb81e-2df1-4801-bec1-c783f1bab69a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_7641426d-7c54-4080-9cf0-9e9ba5e7fb78" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a1afb81e-2df1-4801-bec1-c783f1bab69a" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_7641426d-7c54-4080-9cf0-9e9ba5e7fb78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_7641426d-7c54-4080-9cf0-9e9ba5e7fb78_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_7641426d-7c54-4080-9cf0-9e9ba5e7fb78" xlink:to="loc_us-gaap_SegmentDomain_7641426d-7c54-4080-9cf0-9e9ba5e7fb78_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_b908224a-1971-4f0b-a71e-4c0da3e09b49" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_7641426d-7c54-4080-9cf0-9e9ba5e7fb78" xlink:to="loc_us-gaap_SegmentDomain_b908224a-1971-4f0b-a71e-4c0da3e09b49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllOtherSegmentsMember_574e15a0-8684-42c7-9c6a-5615c13d9f0d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllOtherSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_b908224a-1971-4f0b-a71e-4c0da3e09b49" xlink:to="loc_us-gaap_AllOtherSegmentsMember_574e15a0-8684-42c7-9c6a-5615c13d9f0d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_0f02d048-816c-426a-8121-90a910a7754b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_fe9e5b14-4457-4fbf-accf-a880114a97ba" xlink:to="loc_us-gaap_NumberOfReportableSegments_0f02d048-816c-426a-8121-90a910a7754b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/SegmentReportingScheduleofSegmentReportingDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#SegmentReportingScheduleofSegmentReportingDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/SegmentReportingScheduleofSegmentReportingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_4f05308a-fc43-4760-9d89-50d05e6cf4a7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a333d1de-8d0c-47e4-9393-3b2a3a4a4355" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_4f05308a-fc43-4760-9d89-50d05e6cf4a7" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a333d1de-8d0c-47e4-9393-3b2a3a4a4355" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_0ed6ad62-f542-4ef7-a4e5-0411c1c712da" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_a333d1de-8d0c-47e4-9393-3b2a3a4a4355" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_0ed6ad62-f542-4ef7-a4e5-0411c1c712da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_0ed6ad62-f542-4ef7-a4e5-0411c1c712da_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_0ed6ad62-f542-4ef7-a4e5-0411c1c712da" xlink:to="loc_us-gaap_SegmentDomain_0ed6ad62-f542-4ef7-a4e5-0411c1c712da_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_c3642be1-5ebf-4cc0-8eb1-90c651f06f7f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_0ed6ad62-f542-4ef7-a4e5-0411c1c712da" xlink:to="loc_us-gaap_SegmentDomain_c3642be1-5ebf-4cc0-8eb1-90c651f06f7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveProductsSegmentMember_8ae5dec7-23f7-4b3c-b8fc-ccb610e2994d" xlink:href="gntx-20240331.xsd#gntx_AutomotiveProductsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_c3642be1-5ebf-4cc0-8eb1-90c651f06f7f" xlink:to="loc_gntx_AutomotiveProductsSegmentMember_8ae5dec7-23f7-4b3c-b8fc-ccb610e2994d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllOtherSegmentsMember_c61fd5cb-f9ae-4e3a-8ce2-15d4af372dc3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllOtherSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_c3642be1-5ebf-4cc0-8eb1-90c651f06f7f" xlink:to="loc_us-gaap_AllOtherSegmentsMember_c61fd5cb-f9ae-4e3a-8ce2-15d4af372dc3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_c3e81d6f-72ac-422c-ab09-c1cd55c9058d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_4f05308a-fc43-4760-9d89-50d05e6cf4a7" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_c3e81d6f-72ac-422c-ab09-c1cd55c9058d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_34a4214e-deb9-48e6-9225-c8c37fd7e71d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_4f05308a-fc43-4760-9d89-50d05e6cf4a7" xlink:to="loc_us-gaap_OperatingIncomeLoss_34a4214e-deb9-48e6-9225-c8c37fd7e71d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/RevenueDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#RevenueDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/RevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_cbc9b33c-822f-4e95-8616-71eb650fc06e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_c2eeed7c-fbed-4194-972d-3d6eb75cf69a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_cbc9b33c-822f-4e95-8616-71eb650fc06e" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_c2eeed7c-fbed-4194-972d-3d6eb75cf69a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_af8ab228-20d9-4227-a18e-c32062af0347" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_c2eeed7c-fbed-4194-972d-3d6eb75cf69a" xlink:to="loc_srt_ProductOrServiceAxis_af8ab228-20d9-4227-a18e-c32062af0347" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_af8ab228-20d9-4227-a18e-c32062af0347_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_af8ab228-20d9-4227-a18e-c32062af0347" xlink:to="loc_srt_ProductsAndServicesDomain_af8ab228-20d9-4227-a18e-c32062af0347_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_27d94501-2f68-4e56-a34e-f702e3fec90b" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_af8ab228-20d9-4227-a18e-c32062af0347" xlink:to="loc_srt_ProductsAndServicesDomain_27d94501-2f68-4e56-a34e-f702e3fec90b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveProductsMember_bb19007f-8de8-4c89-b7af-52ef551fc8da" xlink:href="gntx-20240331.xsd#gntx_AutomotiveProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_27d94501-2f68-4e56-a34e-f702e3fec90b" xlink:to="loc_gntx_AutomotiveProductsMember_bb19007f-8de8-4c89-b7af-52ef551fc8da" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveMirrorsElectronicsMember_aa7fac7e-8ebd-4b9a-a958-acbf4fb14071" xlink:href="gntx-20240331.xsd#gntx_AutomotiveMirrorsElectronicsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_AutomotiveProductsMember_bb19007f-8de8-4c89-b7af-52ef551fc8da" xlink:to="loc_gntx_AutomotiveMirrorsElectronicsMember_aa7fac7e-8ebd-4b9a-a958-acbf4fb14071" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_HomeLinkModulesMember_b4833cfb-f8d1-4cc0-aad9-93e1278ed639" xlink:href="gntx-20240331.xsd#gntx_HomeLinkModulesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_AutomotiveProductsMember_bb19007f-8de8-4c89-b7af-52ef551fc8da" xlink:to="loc_gntx_HomeLinkModulesMember_b4833cfb-f8d1-4cc0-aad9-93e1278ed639" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OtherProductsMember_50995293-dc34-49d3-9a77-e48431eb4e77" xlink:href="gntx-20240331.xsd#gntx_OtherProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_27d94501-2f68-4e56-a34e-f702e3fec90b" xlink:to="loc_gntx_OtherProductsMember_50995293-dc34-49d3-9a77-e48431eb4e77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_FireProtectionProductsMember_5d858f05-2828-421d-9e36-c745f367fb59" xlink:href="gntx-20240331.xsd#gntx_FireProtectionProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_OtherProductsMember_50995293-dc34-49d3-9a77-e48431eb4e77" xlink:to="loc_gntx_FireProtectionProductsMember_5d858f05-2828-421d-9e36-c745f367fb59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AerospaceProductsMember_47499a7e-fb33-4221-9911-7ba303d4ecb6" xlink:href="gntx-20240331.xsd#gntx_AerospaceProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_OtherProductsMember_50995293-dc34-49d3-9a77-e48431eb4e77" xlink:to="loc_gntx_AerospaceProductsMember_47499a7e-fb33-4221-9911-7ba303d4ecb6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_MedicalProductMember_a0a78fa3-27a7-4256-88e8-41da673b4b84" xlink:href="gntx-20240331.xsd#gntx_MedicalProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_OtherProductsMember_50995293-dc34-49d3-9a77-e48431eb4e77" xlink:to="loc_gntx_MedicalProductMember_a0a78fa3-27a7-4256-88e8-41da673b4b84" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_40637a5b-c2e4-4479-b942-4c3df95517f6" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_c2eeed7c-fbed-4194-972d-3d6eb75cf69a" xlink:to="loc_srt_StatementGeographicalAxis_40637a5b-c2e4-4479-b942-4c3df95517f6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_40637a5b-c2e4-4479-b942-4c3df95517f6_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_40637a5b-c2e4-4479-b942-4c3df95517f6" xlink:to="loc_srt_SegmentGeographicalDomain_40637a5b-c2e4-4479-b942-4c3df95517f6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_04e19f38-6991-4c1f-b044-352a9ac8f2ed" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_40637a5b-c2e4-4479-b942-4c3df95517f6" xlink:to="loc_srt_SegmentGeographicalDomain_04e19f38-6991-4c1f-b044-352a9ac8f2ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_44a08ab7-82d3-4ca4-aad9-fa40f67fff44" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_04e19f38-6991-4c1f-b044-352a9ac8f2ed" xlink:to="loc_country_US_44a08ab7-82d3-4ca4-aad9-fa40f67fff44" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_JP_d1cad331-3462-4ecb-b824-38a6e90c9c04" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_JP"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_04e19f38-6991-4c1f-b044-352a9ac8f2ed" xlink:to="loc_country_JP_d1cad331-3462-4ecb-b824-38a6e90c9c04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_DE_2181319e-997d-4095-b60f-8fbf7cba9e9c" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_DE"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_04e19f38-6991-4c1f-b044-352a9ac8f2ed" xlink:to="loc_country_DE_2181319e-997d-4095-b60f-8fbf7cba9e9c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_KR_71a82375-8879-4874-91b8-1b9e40d2e41c" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_KR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_04e19f38-6991-4c1f-b044-352a9ac8f2ed" xlink:to="loc_country_KR_71a82375-8879-4874-91b8-1b9e40d2e41c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_MX_1ae78a3d-b414-40c4-b8e0-76ff6b4bf298" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_MX"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_04e19f38-6991-4c1f-b044-352a9ac8f2ed" xlink:to="loc_country_MX_1ae78a3d-b414-40c4-b8e0-76ff6b4bf298" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OtherCountriesMember_05ab563a-501d-440a-9e18-d819029ca1f9" xlink:href="gntx-20240331.xsd#gntx_OtherCountriesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_04e19f38-6991-4c1f-b044-352a9ac8f2ed" xlink:to="loc_gntx_OtherCountriesMember_05ab563a-501d-440a-9e18-d819029ca1f9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_2533d1b3-e0e2-4740-a4a8-e9f8b9868fce" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_c2eeed7c-fbed-4194-972d-3d6eb75cf69a" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_2533d1b3-e0e2-4740-a4a8-e9f8b9868fce" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_2533d1b3-e0e2-4740-a4a8-e9f8b9868fce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_2533d1b3-e0e2-4740-a4a8-e9f8b9868fce" xlink:to="loc_us-gaap_SegmentDomain_2533d1b3-e0e2-4740-a4a8-e9f8b9868fce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_f64e200f-6b07-46c1-a25c-a273cad5006e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_2533d1b3-e0e2-4740-a4a8-e9f8b9868fce" xlink:to="loc_us-gaap_SegmentDomain_f64e200f-6b07-46c1-a25c-a273cad5006e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveSegmentMember_82ddb102-c09f-4e61-b037-a3657b569bc1" xlink:href="gntx-20240331.xsd#gntx_AutomotiveSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f64e200f-6b07-46c1-a25c-a273cad5006e" xlink:to="loc_gntx_AutomotiveSegmentMember_82ddb102-c09f-4e61-b037-a3657b569bc1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OtherSegmentMember_276c993d-2f02-406c-a085-b7f239f1ebf0" xlink:href="gntx-20240331.xsd#gntx_OtherSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f64e200f-6b07-46c1-a25c-a273cad5006e" xlink:to="loc_gntx_OtherSegmentMember_276c993d-2f02-406c-a085-b7f239f1ebf0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_f7c1f070-f4e5-4c47-ae5f-2a7bf6005c04" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_cbc9b33c-822f-4e95-8616-71eb650fc06e" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_f7c1f070-f4e5-4c47-ae5f-2a7bf6005c04" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/LeasesNarrativeDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#LeasesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/LeasesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_6375df43-8300-4534-bfcb-a91b6c8a122e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_69267f38-d315-4427-91f5-f10c645ffdfd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_6375df43-8300-4534-bfcb-a91b6c8a122e" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_69267f38-d315-4427-91f5-f10c645ffdfd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_45ae49ae-5957-42b6-985f-4b5c802ccff7" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_69267f38-d315-4427-91f5-f10c645ffdfd" xlink:to="loc_srt_RangeAxis_45ae49ae-5957-42b6-985f-4b5c802ccff7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_45ae49ae-5957-42b6-985f-4b5c802ccff7_default" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_45ae49ae-5957-42b6-985f-4b5c802ccff7" xlink:to="loc_srt_RangeMember_45ae49ae-5957-42b6-985f-4b5c802ccff7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_b47e8a7b-d4bc-46a8-aba7-65cc73b23cb8" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_45ae49ae-5957-42b6-985f-4b5c802ccff7" xlink:to="loc_srt_RangeMember_b47e8a7b-d4bc-46a8-aba7-65cc73b23cb8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_d3e10f9a-e358-47c9-88f7-071d1cefc327" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_b47e8a7b-d4bc-46a8-aba7-65cc73b23cb8" xlink:to="loc_srt_MinimumMember_d3e10f9a-e358-47c9-88f7-071d1cefc327" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_96d65d6b-c69d-431e-8e45-32ec59b3ed9e" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_b47e8a7b-d4bc-46a8-aba7-65cc73b23cb8" xlink:to="loc_srt_MaximumMember_96d65d6b-c69d-431e-8e45-32ec59b3ed9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_763a6c3b-4c4b-43fe-a7fa-50a116d65b3a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LesseeOperatingLeaseRemainingLeaseTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_6375df43-8300-4534-bfcb-a91b6c8a122e" xlink:to="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_763a6c3b-4c4b-43fe-a7fa-50a116d65b3a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_e2868498-ce74-4600-bd40-d1a2ac765347" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_6375df43-8300-4534-bfcb-a91b6c8a122e" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_e2868498-ce74-4600-bd40-d1a2ac765347" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_f2ed3672-b604-490b-a83d-b9844e0b63aa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_6375df43-8300-4534-bfcb-a91b6c8a122e" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_f2ed3672-b604-490b-a83d-b9844e0b63aa" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/AcquisitionNarrativeDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#AcquisitionNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/AcquisitionNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_44f29103-6d9f-4f0c-9005-a245bef7c1c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a38a08e5-2240-4c6b-bd86-0e4935595bc3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_44f29103-6d9f-4f0c-9005-a245bef7c1c8" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a38a08e5-2240-4c6b-bd86-0e4935595bc3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_b9a2546b-e2cb-49f1-8dcf-d7bf9c071bdf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a38a08e5-2240-4c6b-bd86-0e4935595bc3" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_b9a2546b-e2cb-49f1-8dcf-d7bf9c071bdf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b9a2546b-e2cb-49f1-8dcf-d7bf9c071bdf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_b9a2546b-e2cb-49f1-8dcf-d7bf9c071bdf" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b9a2546b-e2cb-49f1-8dcf-d7bf9c071bdf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6428689e-7c6f-4715-99b8-776c57fcc5d3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_b9a2546b-e2cb-49f1-8dcf-d7bf9c071bdf" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6428689e-7c6f-4715-99b8-776c57fcc5d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ESightCorporationMember_3ab69def-6ef8-4609-977d-a2ff69b50097" xlink:href="gntx-20240331.xsd#gntx_ESightCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6428689e-7c6f-4715-99b8-776c57fcc5d3" xlink:to="loc_gntx_ESightCorporationMember_3ab69def-6ef8-4609-977d-a2ff69b50097" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_b7ea3b0a-3812-4089-9d9d-4a172240ccf9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_44f29103-6d9f-4f0c-9005-a245bef7c1c8" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_b7ea3b0a-3812-4089-9d9d-4a172240ccf9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_829a6dbf-b813-4fc8-bdd5-f9edf143b4d4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_44f29103-6d9f-4f0c-9005-a245bef7c1c8" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_829a6dbf-b813-4fc8-bdd5-f9edf143b4d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_BusinessAcquisitionOwnershipInterestInAcquireeHeldPriorToAcquisition_b633cdad-fd70-4e94-b941-8ecde990054c" xlink:href="gntx-20240331.xsd#gntx_BusinessAcquisitionOwnershipInterestInAcquireeHeldPriorToAcquisition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_44f29103-6d9f-4f0c-9005-a245bef7c1c8" xlink:to="loc_gntx_BusinessAcquisitionOwnershipInterestInAcquireeHeldPriorToAcquisition_b633cdad-fd70-4e94-b941-8ecde990054c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_BusinessCombinationBusinessCombinationContingentConsiderationArrangementsTerm_1bc21437-924a-4070-8785-621032b548a9" xlink:href="gntx-20240331.xsd#gntx_BusinessCombinationBusinessCombinationContingentConsiderationArrangementsTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_44f29103-6d9f-4f0c-9005-a245bef7c1c8" xlink:to="loc_gntx_BusinessCombinationBusinessCombinationContingentConsiderationArrangementsTerm_1bc21437-924a-4070-8785-621032b548a9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh_54f9d42a-2f3a-4db3-8dc9-88b7aa3e55d7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_44f29103-6d9f-4f0c-9005-a245bef7c1c8" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh_54f9d42a-2f3a-4db3-8dc9-88b7aa3e55d7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_94782727-7990-411c-8548-b5ad26d07b9f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_44f29103-6d9f-4f0c-9005-a245bef7c1c8" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_94782727-7990-411c-8548-b5ad26d07b9f" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/AcquisitionScheduleofAssetsAcquiredandLiabilitiesAssumedDetails" xlink:type="simple" xlink:href="gntx-20240331.xsd#AcquisitionScheduleofAssetsAcquiredandLiabilitiesAssumedDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/AcquisitionScheduleofAssetsAcquiredandLiabilitiesAssumedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_6862205e-951c-4846-989a-dc96dc7e25e6" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_14f55274-98c6-4f14-bc4e-af2a8b145d2f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6862205e-951c-4846-989a-dc96dc7e25e6" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_14f55274-98c6-4f14-bc4e-af2a8b145d2f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_11dfb560-5964-494f-9819-649682aefb15" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_14f55274-98c6-4f14-bc4e-af2a8b145d2f" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_11dfb560-5964-494f-9819-649682aefb15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_11dfb560-5964-494f-9819-649682aefb15_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_11dfb560-5964-494f-9819-649682aefb15" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_11dfb560-5964-494f-9819-649682aefb15_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2c57e23e-050b-4b60-8830-b0dcf6385214" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_11dfb560-5964-494f-9819-649682aefb15" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2c57e23e-050b-4b60-8830-b0dcf6385214" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ESightCorporationMember_77233b53-0a7d-45b8-8b0f-898b807e2c46" xlink:href="gntx-20240331.xsd#gntx_ESightCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2c57e23e-050b-4b60-8830-b0dcf6385214" xlink:to="loc_gntx_ESightCorporationMember_77233b53-0a7d-45b8-8b0f-898b807e2c46" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_9046726f-275b-4ed8-90bf-e0a2d1e2a4c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_14f55274-98c6-4f14-bc4e-af2a8b145d2f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_9046726f-275b-4ed8-90bf-e0a2d1e2a4c2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9046726f-275b-4ed8-90bf-e0a2d1e2a4c2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_9046726f-275b-4ed8-90bf-e0a2d1e2a4c2" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9046726f-275b-4ed8-90bf-e0a2d1e2a4c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_cd575675-66a0-48a2-b2cf-7f29eba50701" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_9046726f-275b-4ed8-90bf-e0a2d1e2a4c2" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_cd575675-66a0-48a2-b2cf-7f29eba50701" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_96bf8548-4136-4238-b740-f007223decb7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_cd575675-66a0-48a2-b2cf-7f29eba50701" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_96bf8548-4136-4238-b740-f007223decb7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_739a4032-50d1-41e2-bf5e-35fcbe85689d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_cd575675-66a0-48a2-b2cf-7f29eba50701" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_739a4032-50d1-41e2-bf5e-35fcbe85689d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_8fdba262-a0b5-4f4a-8ec1-a30ff19f008f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6862205e-951c-4846-989a-dc96dc7e25e6" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_8fdba262-a0b5-4f4a-8ec1-a30ff19f008f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_062a6227-3991-449d-90c4-7aeede697cec" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6862205e-951c-4846-989a-dc96dc7e25e6" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_062a6227-3991-449d-90c4-7aeede697cec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseRightOfUseAsset_c5f5a896-26be-450a-894f-097611f97890" xlink:href="gntx-20240331.xsd#gntx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6862205e-951c-4846-989a-dc96dc7e25e6" xlink:to="loc_gntx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseRightOfUseAsset_c5f5a896-26be-450a-894f-097611f97890" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_f7755271-a1fa-475a-a68b-64ceb323be18" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6862205e-951c-4846-989a-dc96dc7e25e6" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_f7755271-a1fa-475a-a68b-64ceb323be18" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_f503b52d-b887-4c73-93cd-f5c511781975" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6862205e-951c-4846-989a-dc96dc7e25e6" xlink:to="loc_us-gaap_Goodwill_f503b52d-b887-4c73-93cd-f5c511781975" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsIncludingGoodwill_73ca402d-b8cf-47bc-9f18-41fa5700271c" xlink:href="gntx-20240331.xsd#gntx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsIncludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6862205e-951c-4846-989a-dc96dc7e25e6" xlink:to="loc_gntx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsIncludingGoodwill_73ca402d-b8cf-47bc-9f18-41fa5700271c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCapitalLeaseObligation_7ae62035-266e-480e-be9c-a799a6fd2f6e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCapitalLeaseObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6862205e-951c-4846-989a-dc96dc7e25e6" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCapitalLeaseObligation_7ae62035-266e-480e-be9c-a799a6fd2f6e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContingentLiability_54a6a608-5f97-4619-a117-dad6db6335fc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContingentLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6862205e-951c-4846-989a-dc96dc7e25e6" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContingentLiability_54a6a608-5f97-4619-a117-dad6db6335fc" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_66acff11-b4a8-4fc5-b58d-4a449acec04e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_6862205e-951c-4846-989a-dc96dc7e25e6" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_66acff11-b4a8-4fc5-b58d-4a449acec04e" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-roles-2023.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent" xlink:type="arc" order="1"/>
  </link:definitionLink>
</link:linkbase>
