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

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:1a5d84a0-7d2f-4c75-916f-8749dafa8c6e,g:e43247da-78da-4af5-a96d-5d3c932f5bcb-->
<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-20220630.xsd#UnauditedCondensedConsolidatedStatementsofShareholdersInvestment"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsofShareholdersInvestment" xlink:type="extended" id="i4b260d87ceed46bbb76f98574dea15ab_UnauditedCondensedConsolidatedStatementsofShareholdersInvestment">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_4988d523-0c89-44c6-8e59-7311e79916d8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4988d523-0c89-44c6-8e59-7311e79916d8" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_123c82b7-0fcf-47bd-9cec-8390c1cf3ccd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_123c82b7-0fcf-47bd-9cec-8390c1cf3ccd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_c1e9f094-728f-4188-801a-c5f7c9ffc983" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:to="loc_us-gaap_StockholdersEquity_c1e9f094-728f-4188-801a-c5f7c9ffc983" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_48448a81-af0d-4aa6-87bf-07c6b099d6b1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_48448a81-af0d-4aa6-87bf-07c6b099d6b1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_f047bf48-77aa-488c-a67f-dde10f6a5d17" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_f047bf48-77aa-488c-a67f-dde10f6a5d17" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_StockIssuedDuringPeriodSharesEquityInvestmentPurchase_2205824f-f000-4c20-af41-5ba880b4eb5b" xlink:href="gntx-20220630.xsd#gntx_StockIssuedDuringPeriodSharesEquityInvestmentPurchase"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:to="loc_gntx_StockIssuedDuringPeriodSharesEquityInvestmentPurchase_2205824f-f000-4c20-af41-5ba880b4eb5b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_StockIssuedDuringPeriodValueEquityInvestmentPurchase_efaf1f07-ddcd-4147-86eb-58a24ae97215" xlink:href="gntx-20220630.xsd#gntx_StockIssuedDuringPeriodValueEquityInvestmentPurchase"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:to="loc_gntx_StockIssuedDuringPeriodValueEquityInvestmentPurchase_efaf1f07-ddcd-4147-86eb-58a24ae97215" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_155705cc-a718-4a30-adaf-0f75f672be10" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_155705cc-a718-4a30-adaf-0f75f672be10" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_36c4ba58-7371-46d4-baf7-0a4340f8fe19" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_36c4ba58-7371-46d4-baf7-0a4340f8fe19" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_d359c258-102e-41fd-ba61-6b56401e5aed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_d359c258-102e-41fd-ba61-6b56401e5aed" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_2642499d-d96b-46ff-90b5-3702618ce0e0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:to="loc_us-gaap_DividendsCommonStockCash_2642499d-d96b-46ff-90b5-3702618ce0e0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_d3819407-df9a-4bfa-aec9-d54e1c3370e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:to="loc_us-gaap_NetIncomeLoss_d3819407-df9a-4bfa-aec9-d54e1c3370e7" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_2a68f331-7d5e-470e-8740-303875577e92" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_01d57caa-106b-413f-98ef-5d3f5b68c5a6" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_2a68f331-7d5e-470e-8740-303875577e92" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_5f7921aa-98a4-445a-9e04-32c2db1ae7d5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_b1685010-8a2e-4eef-b2c2-25b818f6e722" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_2eeadb95-c304-4427-9a88-bc9c83979fe9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_4988d523-0c89-44c6-8e59-7311e79916d8" xlink:to="loc_us-gaap_StatementTable_2eeadb95-c304-4427-9a88-bc9c83979fe9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_1a9effb8-7c93-4dc9-a1f2-ea064f7764a8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_2eeadb95-c304-4427-9a88-bc9c83979fe9" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_1a9effb8-7c93-4dc9-a1f2-ea064f7764a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_1a9effb8-7c93-4dc9-a1f2-ea064f7764a8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_1a9effb8-7c93-4dc9-a1f2-ea064f7764a8" xlink:to="loc_us-gaap_EquityComponentDomain_1a9effb8-7c93-4dc9-a1f2-ea064f7764a8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_06af8d49-380c-4a82-b4fd-ecc41d4c2dd7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_1a9effb8-7c93-4dc9-a1f2-ea064f7764a8" xlink:to="loc_us-gaap_EquityComponentDomain_06af8d49-380c-4a82-b4fd-ecc41d4c2dd7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_8fcb05f1-e1ce-4daa-bdc6-bb9047b4e67e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_06af8d49-380c-4a82-b4fd-ecc41d4c2dd7" xlink:to="loc_us-gaap_CommonStockMember_8fcb05f1-e1ce-4daa-bdc6-bb9047b4e67e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_c9407e18-cecc-4911-85bb-92c719ed7ea9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_06af8d49-380c-4a82-b4fd-ecc41d4c2dd7" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_c9407e18-cecc-4911-85bb-92c719ed7ea9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_1604eee7-15c8-47ed-8477-923e157f7b86" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_06af8d49-380c-4a82-b4fd-ecc41d4c2dd7" xlink:to="loc_us-gaap_RetainedEarningsMember_1604eee7-15c8-47ed-8477-923e157f7b86" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_8da90abb-0466-48a8-9a38-14a779bde9ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_06af8d49-380c-4a82-b4fd-ecc41d4c2dd7" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_8da90abb-0466-48a8-9a38-14a779bde9ec" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#GoodwillandOtherIntangibleAssetsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="extended" id="idbde50e53c294ab398ec5e4e09c47856_GoodwillandOtherIntangibleAssetsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_89c5f64a-3c90-404a-bc04-77a5ee67dab2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_286f5264-5318-4444-846a-83e141824fdd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_89c5f64a-3c90-404a-bc04-77a5ee67dab2" xlink:to="loc_us-gaap_Goodwill_286f5264-5318-4444-846a-83e141824fdd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAcquiredDuringPeriod_4f327683-b918-4bda-8642-c97153387f1d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GoodwillAcquiredDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_89c5f64a-3c90-404a-bc04-77a5ee67dab2" xlink:to="loc_us-gaap_GoodwillAcquiredDuringPeriod_4f327683-b918-4bda-8642-c97153387f1d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_2eea0e53-5ff8-49cf-9465-ea49f9bdbc77" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_89c5f64a-3c90-404a-bc04-77a5ee67dab2" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_2eea0e53-5ff8-49cf-9465-ea49f9bdbc77" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_645bba42-d437-416b-beaa-ef169ca03af3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_89c5f64a-3c90-404a-bc04-77a5ee67dab2" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_645bba42-d437-416b-beaa-ef169ca03af3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_48b42978-9f0c-482d-bfa0-b0e49737fae3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_89c5f64a-3c90-404a-bc04-77a5ee67dab2" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_48b42978-9f0c-482d-bfa0-b0e49737fae3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_b8059564-f4bc-4452-8f60-7f8640695c06" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_89c5f64a-3c90-404a-bc04-77a5ee67dab2" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_b8059564-f4bc-4452-8f60-7f8640695c06" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_4822d55f-ae16-444b-833b-4b163f85e2a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_89c5f64a-3c90-404a-bc04-77a5ee67dab2" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_4822d55f-ae16-444b-833b-4b163f85e2a9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_6c8bcca5-b5e1-4d52-b6ee-99d27dce7c88" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_89c5f64a-3c90-404a-bc04-77a5ee67dab2" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_6c8bcca5-b5e1-4d52-b6ee-99d27dce7c88" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_5cec331d-a7a7-4eca-847b-a30940612f36" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_89c5f64a-3c90-404a-bc04-77a5ee67dab2" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_5cec331d-a7a7-4eca-847b-a30940612f36" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_9a5d026e-779c-495c-88db-b13a4f1c0ae8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_5cec331d-a7a7-4eca-847b-a30940612f36" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_9a5d026e-779c-495c-88db-b13a4f1c0ae8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9a5d026e-779c-495c-88db-b13a4f1c0ae8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_9a5d026e-779c-495c-88db-b13a4f1c0ae8" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9a5d026e-779c-495c-88db-b13a4f1c0ae8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_54c5182b-ca42-4a71-a983-557260e29612" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_9a5d026e-779c-495c-88db-b13a4f1c0ae8" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_54c5182b-ca42-4a71-a983-557260e29612" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_HomeLinkMember_75c9303f-61ea-4ed2-963e-01b27437b34d" xlink:href="gntx-20220630.xsd#gntx_HomeLinkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_54c5182b-ca42-4a71-a983-557260e29612" xlink:to="loc_gntx_HomeLinkMember_75c9303f-61ea-4ed2-963e-01b27437b34d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_VaporsensIncMember_15a127b5-5e23-4266-9d4d-35370b60614a" xlink:href="gntx-20220630.xsd#gntx_VaporsensIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_54c5182b-ca42-4a71-a983-557260e29612" xlink:to="loc_gntx_VaporsensIncMember_15a127b5-5e23-4266-9d4d-35370b60614a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AirCraftGlassMember_85fb39a4-bf4a-48f3-8316-68ac2932a778" xlink:href="gntx-20220630.xsd#gntx_AirCraftGlassMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_54c5182b-ca42-4a71-a983-557260e29612" xlink:to="loc_gntx_AirCraftGlassMember_85fb39a4-bf4a-48f3-8316-68ac2932a778" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ArgilIncMember_8da9f33d-5dbf-44b6-95d8-d1761853905e" xlink:href="gntx-20220630.xsd#gntx_ArgilIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_54c5182b-ca42-4a71-a983-557260e29612" xlink:to="loc_gntx_ArgilIncMember_8da9f33d-5dbf-44b6-95d8-d1761853905e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_GuardianOpticalTechnologiesMember_a7754ac7-cb7a-4ed0-9951-99eae608e8a3" xlink:href="gntx-20220630.xsd#gntx_GuardianOpticalTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_54c5182b-ca42-4a71-a983-557260e29612" xlink:to="loc_gntx_GuardianOpticalTechnologiesMember_a7754ac7-cb7a-4ed0-9951-99eae608e8a3" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails" xlink:type="extended" id="ib9e5a645c8534b51905d090cb209068e_GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b83ce2cf-e3b3-44d7-9a8a-4a5c50ccf8f6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_4b2ebf82-fb0e-4fb4-b788-6b7266adf814" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b83ce2cf-e3b3-44d7-9a8a-4a5c50ccf8f6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_4b2ebf82-fb0e-4fb4-b788-6b7266adf814" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_46358290-00bb-4a0c-bd82-7275b44fdbc6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b83ce2cf-e3b3-44d7-9a8a-4a5c50ccf8f6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_46358290-00bb-4a0c-bd82-7275b44fdbc6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_bf31ed38-2e70-42fc-80f4-723d3822e248" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b83ce2cf-e3b3-44d7-9a8a-4a5c50ccf8f6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_bf31ed38-2e70-42fc-80f4-723d3822e248" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_ac2ec5be-0d06-48ee-a56b-3f728a10c444" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b83ce2cf-e3b3-44d7-9a8a-4a5c50ccf8f6" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_ac2ec5be-0d06-48ee-a56b-3f728a10c444" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_a43ff297-3c83-4cb9-8d8d-5a36eed7d3ae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b83ce2cf-e3b3-44d7-9a8a-4a5c50ccf8f6" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_a43ff297-3c83-4cb9-8d8d-5a36eed7d3ae" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_ea8c879d-2e60-4100-bdcd-ae8d33d2c25f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b83ce2cf-e3b3-44d7-9a8a-4a5c50ccf8f6" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_ea8c879d-2e60-4100-bdcd-ae8d33d2c25f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_IntangiblePatentsAndAssetsGrossExcludingGoodwill_6410499f-d69b-4548-9953-12fd29688899" xlink:href="gntx-20220630.xsd#gntx_IntangiblePatentsAndAssetsGrossExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b83ce2cf-e3b3-44d7-9a8a-4a5c50ccf8f6" xlink:to="loc_gntx_IntangiblePatentsAndAssetsGrossExcludingGoodwill_6410499f-d69b-4548-9953-12fd29688899" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_FiniteLivedIntangiblePatentsAndAssetsAccumulatedAmortization_ba4b04f2-80d8-4765-b6ae-7da42f9bf2d8" xlink:href="gntx-20220630.xsd#gntx_FiniteLivedIntangiblePatentsAndAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b83ce2cf-e3b3-44d7-9a8a-4a5c50ccf8f6" xlink:to="loc_gntx_FiniteLivedIntangiblePatentsAndAssetsAccumulatedAmortization_ba4b04f2-80d8-4765-b6ae-7da42f9bf2d8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_IntangiblePatentsAndAssetsNetExcludingGoodwill_6f914543-677c-4863-bf1c-c4765d5d9317" xlink:href="gntx-20220630.xsd#gntx_IntangiblePatentsAndAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b83ce2cf-e3b3-44d7-9a8a-4a5c50ccf8f6" xlink:to="loc_gntx_IntangiblePatentsAndAssetsNetExcludingGoodwill_6f914543-677c-4863-bf1c-c4765d5d9317" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_df22c293-6b94-4a84-9dbc-0d24a10208fd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b83ce2cf-e3b3-44d7-9a8a-4a5c50ccf8f6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_df22c293-6b94-4a84-9dbc-0d24a10208fd" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_7840e03d-f010-4845-b5ff-fabf72d55d3f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_b83ce2cf-e3b3-44d7-9a8a-4a5c50ccf8f6" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_7840e03d-f010-4845-b5ff-fabf72d55d3f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_5782dc73-a406-4a14-943d-a9f37e25441a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_7840e03d-f010-4845-b5ff-fabf72d55d3f" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_5782dc73-a406-4a14-943d-a9f37e25441a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_5782dc73-a406-4a14-943d-a9f37e25441a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_5782dc73-a406-4a14-943d-a9f37e25441a" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_5782dc73-a406-4a14-943d-a9f37e25441a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_55735ad6-36f1-4c91-9984-510f30ccd203" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_5782dc73-a406-4a14-943d-a9f37e25441a" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_55735ad6-36f1-4c91-9984-510f30ccd203" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_4b478ecc-dca4-4a00-b3bf-373a2106d136" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_55735ad6-36f1-4c91-9984-510f30ccd203" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_4b478ecc-dca4-4a00-b3bf-373a2106d136" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LicensingAgreementsMember_55d61312-2dc4-4b5a-bbfb-3ca9305bec14" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LicensingAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_55735ad6-36f1-4c91-9984-510f30ccd203" xlink:to="loc_us-gaap_LicensingAgreementsMember_55d61312-2dc4-4b5a-bbfb-3ca9305bec14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InProcessResearchAndDevelopmentMember_276e442b-3c11-44e2-bfd1-2e3735d67a7d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InProcessResearchAndDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_55735ad6-36f1-4c91-9984-510f30ccd203" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_276e442b-3c11-44e2-bfd1-2e3735d67a7d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_f86035a7-1022-4fb2-8182-3bd73369d418" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_7840e03d-f010-4845-b5ff-fabf72d55d3f" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_f86035a7-1022-4fb2-8182-3bd73369d418" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f86035a7-1022-4fb2-8182-3bd73369d418_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_f86035a7-1022-4fb2-8182-3bd73369d418" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f86035a7-1022-4fb2-8182-3bd73369d418_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7900529a-e8e5-45d5-8fda-5b510b0a1449" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_f86035a7-1022-4fb2-8182-3bd73369d418" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7900529a-e8e5-45d5-8fda-5b510b0a1449" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_PatentsAndOtherIntangibleAssetsMember_6cdb9308-86f4-4ea4-a2ab-0ab6b22088d6" xlink:href="gntx-20220630.xsd#gntx_PatentsAndOtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7900529a-e8e5-45d5-8fda-5b510b0a1449" xlink:to="loc_gntx_PatentsAndOtherIntangibleAssetsMember_6cdb9308-86f4-4ea4-a2ab-0ab6b22088d6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentsMember_af30f032-700b-44c5-a750-ede51c622860" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PatentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7900529a-e8e5-45d5-8fda-5b510b0a1449" xlink:to="loc_us-gaap_PatentsMember_af30f032-700b-44c5-a750-ede51c622860" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_f41da6a5-8900-4cbc-a4fb-13898309b242" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TechnologyBasedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7900529a-e8e5-45d5-8fda-5b510b0a1449" xlink:to="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_f41da6a5-8900-4cbc-a4fb-13898309b242" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_dcfca734-a606-454f-90d7-0e1b859b7bc9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7900529a-e8e5-45d5-8fda-5b510b0a1449" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_dcfca734-a606-454f-90d7-0e1b859b7bc9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerContractsMember_64f019ca-6f3c-4497-a873-e1ccc6feb837" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CustomerContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7900529a-e8e5-45d5-8fda-5b510b0a1449" xlink:to="loc_us-gaap_CustomerContractsMember_64f019ca-6f3c-4497-a873-e1ccc6feb837" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_c6bfc68e-77f3-4849-911c-172b03806566" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7900529a-e8e5-45d5-8fda-5b510b0a1449" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_c6bfc68e-77f3-4849-911c-172b03806566" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_ec5c2662-4494-4407-894e-888de67bfb8c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_7840e03d-f010-4845-b5ff-fabf72d55d3f" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_ec5c2662-4494-4407-894e-888de67bfb8c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ec5c2662-4494-4407-894e-888de67bfb8c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_ec5c2662-4494-4407-894e-888de67bfb8c" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ec5c2662-4494-4407-894e-888de67bfb8c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d7686f6f-912e-4987-a3a7-62aa28160db5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_ec5c2662-4494-4407-894e-888de67bfb8c" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d7686f6f-912e-4987-a3a7-62aa28160db5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_VaporsensIncMember_f6a4d5fc-e1bb-47fc-86b7-f51afb3bb1e0" xlink:href="gntx-20220630.xsd#gntx_VaporsensIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d7686f6f-912e-4987-a3a7-62aa28160db5" xlink:to="loc_gntx_VaporsensIncMember_f6a4d5fc-e1bb-47fc-86b7-f51afb3bb1e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ArgilIncMember_7deb813c-e109-4636-9c0f-d6932a14d5b3" xlink:href="gntx-20220630.xsd#gntx_ArgilIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d7686f6f-912e-4987-a3a7-62aa28160db5" xlink:to="loc_gntx_ArgilIncMember_7deb813c-e109-4636-9c0f-d6932a14d5b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AirCraftGlassMember_d5c36337-fabc-4236-9813-9a603b3ce69c" xlink:href="gntx-20220630.xsd#gntx_AirCraftGlassMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d7686f6f-912e-4987-a3a7-62aa28160db5" xlink:to="loc_gntx_AirCraftGlassMember_d5c36337-fabc-4236-9813-9a603b3ce69c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_GuardianOpticalTechnologiesMember_7bd5b152-0a31-4135-8b22-54ad6380caaa" xlink:href="gntx-20220630.xsd#gntx_GuardianOpticalTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d7686f6f-912e-4987-a3a7-62aa28160db5" xlink:to="loc_gntx_GuardianOpticalTechnologiesMember_7bd5b152-0a31-4135-8b22-54ad6380caaa" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsNarrativeDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#InvestmentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsNarrativeDetails" xlink:type="extended" id="i5c2aae2576924a569d816a532a9ac1fd_InvestmentsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a6477aa2-334e-4e32-a01b-84fc59079ae0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_b83d06f8-44f7-42b7-8044-d990e6924365" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a6477aa2-334e-4e32-a01b-84fc59079ae0" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_b83d06f8-44f7-42b7-8044-d990e6924365" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_9dda9ad2-29f8-4143-9d4d-8776b7fb03b4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a6477aa2-334e-4e32-a01b-84fc59079ae0" xlink:to="loc_us-gaap_EquityMethodInvestments_9dda9ad2-29f8-4143-9d4d-8776b7fb03b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_8e91e745-3471-4e5b-a23c-7e4c8c050ca0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a6477aa2-334e-4e32-a01b-84fc59079ae0" xlink:to="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_8e91e745-3471-4e5b-a23c-7e4c8c050ca0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfInvestments_df2a6362-8f74-40d7-94e8-9fb226d24913" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ImpairmentOfInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a6477aa2-334e-4e32-a01b-84fc59079ae0" xlink:to="loc_us-gaap_ImpairmentOfInvestments_df2a6362-8f74-40d7-94e8-9fb226d24913" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_5b2e2100-f4c3-4b51-8d23-4d90bdcb0bca" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_a6477aa2-334e-4e32-a01b-84fc59079ae0" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_5b2e2100-f4c3-4b51-8d23-4d90bdcb0bca" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_4bf93b64-3afd-4e8e-83ab-c230ec27219f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_5b2e2100-f4c3-4b51-8d23-4d90bdcb0bca" xlink:to="loc_srt_RangeAxis_4bf93b64-3afd-4e8e-83ab-c230ec27219f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_4bf93b64-3afd-4e8e-83ab-c230ec27219f_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_4bf93b64-3afd-4e8e-83ab-c230ec27219f" xlink:to="loc_srt_RangeMember_4bf93b64-3afd-4e8e-83ab-c230ec27219f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_5ff0d118-564b-4f23-80b3-9a5bcaecd8f7" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_4bf93b64-3afd-4e8e-83ab-c230ec27219f" xlink:to="loc_srt_RangeMember_5ff0d118-564b-4f23-80b3-9a5bcaecd8f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_194a6310-627f-47b5-9109-60908ad34e23" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5ff0d118-564b-4f23-80b3-9a5bcaecd8f7" xlink:to="loc_srt_MinimumMember_194a6310-627f-47b5-9109-60908ad34e23" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_c731b51e-7fcc-48cd-b343-fdb15e604535" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5ff0d118-564b-4f23-80b3-9a5bcaecd8f7" xlink:to="loc_srt_MaximumMember_c731b51e-7fcc-48cd-b343-fdb15e604535" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_b9d82aa8-5dc3-40aa-ba30-d48e1ce46fe3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_5b2e2100-f4c3-4b51-8d23-4d90bdcb0bca" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_b9d82aa8-5dc3-40aa-ba30-d48e1ce46fe3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_b9d82aa8-5dc3-40aa-ba30-d48e1ce46fe3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_b9d82aa8-5dc3-40aa-ba30-d48e1ce46fe3" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_b9d82aa8-5dc3-40aa-ba30-d48e1ce46fe3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_e0bd833f-d1b8-4946-b0fc-916bd01e3af7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_b9d82aa8-5dc3-40aa-ba30-d48e1ce46fe3" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_e0bd833f-d1b8-4946-b0fc-916bd01e3af7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_LongTermInvestmentsMember_151a1f8a-c524-4f0b-9969-e42fed39fa47" xlink:href="gntx-20220630.xsd#gntx_LongTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e0bd833f-d1b8-4946-b0fc-916bd01e3af7" xlink:to="loc_gntx_LongTermInvestmentsMember_151a1f8a-c524-4f0b-9969-e42fed39fa47" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_0b052abf-9d62-4a0e-9b1c-e461a4e1c1c0" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_5b2e2100-f4c3-4b51-8d23-4d90bdcb0bca" xlink:to="loc_srt_OwnershipAxis_0b052abf-9d62-4a0e-9b1c-e461a4e1c1c0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_0b052abf-9d62-4a0e-9b1c-e461a4e1c1c0_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_0b052abf-9d62-4a0e-9b1c-e461a4e1c1c0" xlink:to="loc_srt_OwnershipDomain_0b052abf-9d62-4a0e-9b1c-e461a4e1c1c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_066c9145-a13f-4621-aa3d-e1cb884cb0eb" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_0b052abf-9d62-4a0e-9b1c-e461a4e1c1c0" xlink:to="loc_srt_OwnershipDomain_066c9145-a13f-4621-aa3d-e1cb884cb0eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_GentexCorporationMember_3362ee0b-0b89-4592-a0d7-f97f4a58cf3d" xlink:href="gntx-20220630.xsd#gntx_GentexCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_066c9145-a13f-4621-aa3d-e1cb884cb0eb" xlink:to="loc_gntx_GentexCorporationMember_3362ee0b-0b89-4592-a0d7-f97f4a58cf3d" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails" xlink:type="extended" id="i52e796e58e2e4aa1887416869d5f392a_InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9e4f57f9-5e02-4a55-890e-77c8e93b90fd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_685aa495-d15e-431d-b94a-4ab13ea172fc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9e4f57f9-5e02-4a55-890e-77c8e93b90fd" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_685aa495-d15e-431d-b94a-4ab13ea172fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_9efc3b19-36e4-4710-8718-e0dfc6e1b0e8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9e4f57f9-5e02-4a55-890e-77c8e93b90fd" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_9efc3b19-36e4-4710-8718-e0dfc6e1b0e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_3ecec85c-31b1-4fc3-bdcd-5acbffb01b36" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9e4f57f9-5e02-4a55-890e-77c8e93b90fd" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_3ecec85c-31b1-4fc3-bdcd-5acbffb01b36" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c007ccd6-caae-416e-b932-266fd48ffda3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_9e4f57f9-5e02-4a55-890e-77c8e93b90fd" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c007ccd6-caae-416e-b932-266fd48ffda3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_be096355-4a2e-4019-92fb-6ae876359167" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c007ccd6-caae-416e-b932-266fd48ffda3" xlink:to="loc_us-gaap_InvestmentTypeAxis_be096355-4a2e-4019-92fb-6ae876359167" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_be096355-4a2e-4019-92fb-6ae876359167_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_be096355-4a2e-4019-92fb-6ae876359167" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_be096355-4a2e-4019-92fb-6ae876359167_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_94067ced-7a09-4ffd-8d75-f9faf6bf3a7d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_be096355-4a2e-4019-92fb-6ae876359167" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_94067ced-7a09-4ffd-8d75-f9faf6bf3a7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_eabea979-e376-46dd-9b73-f49ff0826677" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_94067ced-7a09-4ffd-8d75-f9faf6bf3a7d" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_eabea979-e376-46dd-9b73-f49ff0826677" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermInvestmentsMember_8aa9e8d1-3d74-4c0b-b175-8771584db535" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLongTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_94067ced-7a09-4ffd-8d75-f9faf6bf3a7d" xlink:to="loc_us-gaap_OtherLongTermInvestmentsMember_8aa9e8d1-3d74-4c0b-b175-8771584db535" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_6cd16c37-bfda-4c2a-a4c3-d7e5e87191e4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c007ccd6-caae-416e-b932-266fd48ffda3" xlink:to="loc_us-gaap_FinancialInstrumentAxis_6cd16c37-bfda-4c2a-a4c3-d7e5e87191e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6cd16c37-bfda-4c2a-a4c3-d7e5e87191e4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_6cd16c37-bfda-4c2a-a4c3-d7e5e87191e4" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6cd16c37-bfda-4c2a-a4c3-d7e5e87191e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_eba2b289-48ed-4216-a424-01d146725c08" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_6cd16c37-bfda-4c2a-a4c3-d7e5e87191e4" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_eba2b289-48ed-4216-a424-01d146725c08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_2f19500c-7996-4924-a0bf-5998ab467bdc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_eba2b289-48ed-4216-a424-01d146725c08" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_2f19500c-7996-4924-a0bf-5998ab467bdc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_c3de7f19-d268-464e-a0e0-91503070cce8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_eba2b289-48ed-4216-a424-01d146725c08" xlink:to="loc_us-gaap_CertificatesOfDepositMember_c3de7f19-d268-464e-a0e0-91503070cce8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_c31a0e69-398e-4fae-8a71-c403a4dcf980" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CorporateBondSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_eba2b289-48ed-4216-a424-01d146725c08" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_c31a0e69-398e-4fae-8a71-c403a4dcf980" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_6f390e91-81e2-47e2-8b7a-98caa2f1aca7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_eba2b289-48ed-4216-a424-01d146725c08" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_6f390e91-81e2-47e2-8b7a-98caa2f1aca7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MunicipalBondsMember_a7bd0b2a-a781-4b69-919b-985d942ea474" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MunicipalBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_eba2b289-48ed-4216-a424-01d146725c08" xlink:to="loc_us-gaap_MunicipalBondsMember_a7bd0b2a-a781-4b69-919b-985d942ea474" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_12dfec67-ef57-4367-9e68-4c36082f0a3d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_eba2b289-48ed-4216-a424-01d146725c08" xlink:to="loc_us-gaap_OtherDebtSecuritiesMember_12dfec67-ef57-4367-9e68-4c36082f0a3d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_804a099a-7b5d-4cad-b683-9e8f7c3dfcbd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c007ccd6-caae-416e-b932-266fd48ffda3" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_804a099a-7b5d-4cad-b683-9e8f7c3dfcbd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_804a099a-7b5d-4cad-b683-9e8f7c3dfcbd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_804a099a-7b5d-4cad-b683-9e8f7c3dfcbd" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_804a099a-7b5d-4cad-b683-9e8f7c3dfcbd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3582a286-337c-4dd8-bcfc-7ca4f6dd3013" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_804a099a-7b5d-4cad-b683-9e8f7c3dfcbd" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3582a286-337c-4dd8-bcfc-7ca4f6dd3013" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_38d4e869-87d8-4117-b63c-208ba0406462" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3582a286-337c-4dd8-bcfc-7ca4f6dd3013" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_38d4e869-87d8-4117-b63c-208ba0406462" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_252e6e6d-e028-4857-9246-f5ffcb3452ab" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3582a286-337c-4dd8-bcfc-7ca4f6dd3013" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_252e6e6d-e028-4857-9246-f5ffcb3452ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_8eed228a-1fe6-4e33-a1bc-f367caba1743" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3582a286-337c-4dd8-bcfc-7ca4f6dd3013" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_8eed228a-1fe6-4e33-a1bc-f367caba1743" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails" xlink:type="extended" id="i373a1ed638224eaf844b952ea11b2a60_InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_739ee63c-a358-4605-b7f8-632fc18ab6d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostCurrent_854b72f1-9cbd-41ec-8d7b-04da8554735a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_739ee63c-a358-4605-b7f8-632fc18ab6d6" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostCurrent_854b72f1-9cbd-41ec-8d7b-04da8554735a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_7d585d35-5d0b-4c87-be85-2cf75c2b2da2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_739ee63c-a358-4605-b7f8-632fc18ab6d6" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_7d585d35-5d0b-4c87-be85-2cf75c2b2da2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_15893adf-27ab-48e4-bb03-b701e2d6c795" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_739ee63c-a358-4605-b7f8-632fc18ab6d6" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_15893adf-27ab-48e4-bb03-b701e2d6c795" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_06974d5a-6cd2-4818-8a36-14b73bfa8d92" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_739ee63c-a358-4605-b7f8-632fc18ab6d6" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_06974d5a-6cd2-4818-8a36-14b73bfa8d92" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_e004da0f-77a1-4b80-be27-954923afdbd4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_739ee63c-a358-4605-b7f8-632fc18ab6d6" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_e004da0f-77a1-4b80-be27-954923afdbd4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_9ad55cde-b04a-4774-8de9-466f990df2d0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_e004da0f-77a1-4b80-be27-954923afdbd4" xlink:to="loc_us-gaap_InvestmentTypeAxis_9ad55cde-b04a-4774-8de9-466f990df2d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_9ad55cde-b04a-4774-8de9-466f990df2d0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_9ad55cde-b04a-4774-8de9-466f990df2d0" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_9ad55cde-b04a-4774-8de9-466f990df2d0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_8fc3432f-97fc-4143-8eef-fb4f550705f0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_9ad55cde-b04a-4774-8de9-466f990df2d0" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_8fc3432f-97fc-4143-8eef-fb4f550705f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_1ec76178-8c18-4f60-b8e3-5ba1148c230e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_8fc3432f-97fc-4143-8eef-fb4f550705f0" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_1ec76178-8c18-4f60-b8e3-5ba1148c230e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermInvestmentsMember_45e6ebc6-8a75-48a2-b5e6-684d173db68d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLongTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_8fc3432f-97fc-4143-8eef-fb4f550705f0" xlink:to="loc_us-gaap_OtherLongTermInvestmentsMember_45e6ebc6-8a75-48a2-b5e6-684d173db68d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_e8790f4d-8cee-41cd-bc38-a2ed0f6a43e5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_e004da0f-77a1-4b80-be27-954923afdbd4" xlink:to="loc_us-gaap_FinancialInstrumentAxis_e8790f4d-8cee-41cd-bc38-a2ed0f6a43e5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e8790f4d-8cee-41cd-bc38-a2ed0f6a43e5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_e8790f4d-8cee-41cd-bc38-a2ed0f6a43e5" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e8790f4d-8cee-41cd-bc38-a2ed0f6a43e5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_258d57fb-f002-45b3-b9f5-61c496653d13" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_e8790f4d-8cee-41cd-bc38-a2ed0f6a43e5" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_258d57fb-f002-45b3-b9f5-61c496653d13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_d6acb631-5068-4664-8caf-5811dfc69e0e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_258d57fb-f002-45b3-b9f5-61c496653d13" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_d6acb631-5068-4664-8caf-5811dfc69e0e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_a336a7f1-f207-41f3-9fe5-82eae94c598b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_258d57fb-f002-45b3-b9f5-61c496653d13" xlink:to="loc_us-gaap_CertificatesOfDepositMember_a336a7f1-f207-41f3-9fe5-82eae94c598b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_44b533fc-47a8-4cd8-bb38-95e02d5bc530" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CorporateBondSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_258d57fb-f002-45b3-b9f5-61c496653d13" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_44b533fc-47a8-4cd8-bb38-95e02d5bc530" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_1dce02ba-b08d-402d-884d-4db9ff8f6002" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_258d57fb-f002-45b3-b9f5-61c496653d13" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_1dce02ba-b08d-402d-884d-4db9ff8f6002" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MunicipalBondsMember_259912b4-245c-4f2f-9f9f-acdc3ded295e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MunicipalBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_258d57fb-f002-45b3-b9f5-61c496653d13" xlink:to="loc_us-gaap_MunicipalBondsMember_259912b4-245c-4f2f-9f9f-acdc3ded295e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_6a053954-4e3f-4d17-8bea-1960cd96e9ac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_258d57fb-f002-45b3-b9f5-61c496653d13" xlink:to="loc_us-gaap_OtherDebtSecuritiesMember_6a053954-4e3f-4d17-8bea-1960cd96e9ac" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsInvestmentsClassifiedbyContractualMaturityDateDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#InvestmentsInvestmentsClassifiedbyContractualMaturityDateDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsInvestmentsClassifiedbyContractualMaturityDateDetails" xlink:type="extended" id="i4ad76bbe2acc4029864e3adcc4fd768e_InvestmentsInvestmentsClassifiedbyContractualMaturityDateDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_2bbbe605-daf9-4ae8-a3e5-c1caae01a6ac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_bdd39237-fd0a-4bf8-a000-63aefa3535d0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_2bbbe605-daf9-4ae8-a3e5-c1caae01a6ac" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_bdd39237-fd0a-4bf8-a000-63aefa3535d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_610e4109-0d78-420a-b333-6d23a35dadc4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_2bbbe605-daf9-4ae8-a3e5-c1caae01a6ac" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_610e4109-0d78-420a-b333-6d23a35dadc4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterFiveYearsFairValue_7fc0161d-f65d-460e-82e3-4005e941dadf" xlink:href="gntx-20220630.xsd#gntx_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_2bbbe605-daf9-4ae8-a3e5-c1caae01a6ac" xlink:to="loc_gntx_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterFiveYearsFairValue_7fc0161d-f65d-460e-82e3-4005e941dadf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_db691acd-2d00-444f-a5cd-e60236346d24" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_2bbbe605-daf9-4ae8-a3e5-c1caae01a6ac" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_db691acd-2d00-444f-a5cd-e60236346d24" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_9e94429d-c655-48bb-a2e6-c2db73cccb30" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_2bbbe605-daf9-4ae8-a3e5-c1caae01a6ac" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_9e94429d-c655-48bb-a2e6-c2db73cccb30" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_8ea7cc19-54ed-4e87-b420-75a770a89605" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_9e94429d-c655-48bb-a2e6-c2db73cccb30" xlink:to="loc_us-gaap_FinancialInstrumentAxis_8ea7cc19-54ed-4e87-b420-75a770a89605" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8ea7cc19-54ed-4e87-b420-75a770a89605_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_8ea7cc19-54ed-4e87-b420-75a770a89605" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8ea7cc19-54ed-4e87-b420-75a770a89605_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_2b7d18ce-b663-4e0f-b5e3-7019d2845520" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_8ea7cc19-54ed-4e87-b420-75a770a89605" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_2b7d18ce-b663-4e0f-b5e3-7019d2845520" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedIncomeSecuritiesMember_8b2c55ef-9347-4e48-a5c3-3884764e00a2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FixedIncomeSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_2b7d18ce-b663-4e0f-b5e3-7019d2845520" xlink:to="loc_us-gaap_FixedIncomeSecuritiesMember_8b2c55ef-9347-4e48-a5c3-3884764e00a2" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlansNarrativeDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#StockBasedCompensationPlansNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlansNarrativeDetails" xlink:type="extended" id="id7168dc9dc0b4f86a8a054c931f84b4a_StockBasedCompensationPlansNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_SharebasedCompensationArrangementbySharebasedPaymentAwardNumberOfPlans_00a43be0-bce4-47f1-8ceb-72da0f35870e" xlink:href="gntx-20220630.xsd#gntx_SharebasedCompensationArrangementbySharebasedPaymentAwardNumberOfPlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:to="loc_gntx_SharebasedCompensationArrangementbySharebasedPaymentAwardNumberOfPlans_00a43be0-bce4-47f1-8ceb-72da0f35870e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_7dce858d-283c-43bf-9358-6558d0ff8525" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_7dce858d-283c-43bf-9358-6558d0ff8525" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod_2e1e9602-f7a5-4381-aa9f-ede701892714" xlink:href="gntx-20220630.xsd#gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod_2e1e9602-f7a5-4381-aa9f-ede701892714" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_cd45453e-5bbf-49b5-bef5-7a8fac5fb597" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_cd45453e-5bbf-49b5-bef5-7a8fac5fb597" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_9e72c590-3084-4e46-9385-826580a662d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_9e72c590-3084-4e46-9385-826580a662d6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_26748d2e-bc77-45f2-99b9-a6a9551c594a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_26748d2e-bc77-45f2-99b9-a6a9551c594a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_2465cb9d-66ef-47f9-9a9e-94660bb4d90f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_2465cb9d-66ef-47f9-9a9e-94660bb4d90f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_39577c60-97e4-4f85-8db3-e043f56c7fcd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_39577c60-97e4-4f85-8db3-e043f56c7fcd" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationRestrictedPeriod_b604b73d-ac43-4a83-89cd-d130ce9ac2f3" xlink:href="gntx-20220630.xsd#gntx_ShareBasedCompensationRestrictedPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:to="loc_gntx_ShareBasedCompensationRestrictedPeriod_b604b73d-ac43-4a83-89cd-d130ce9ac2f3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockExpense_2efed488-fba8-4074-98f2-5007caabaca5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:to="loc_us-gaap_RestrictedStockExpense_2efed488-fba8-4074-98f2-5007caabaca5" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_f1974efe-3677-466d-99bc-87e3e930616e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_f1974efe-3677-466d-99bc-87e3e930616e" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense_5b53c891-3e85-4e0d-8ce9-a30f556c4000" xlink:href="gntx-20220630.xsd#gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense_5b53c891-3e85-4e0d-8ce9-a30f556c4000" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bb77c6eb-0e6b-4187-a2a8-fc34a526d9a5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7eacab9f-ccd7-4609-8e4c-6880829c4793" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bb77c6eb-0e6b-4187-a2a8-fc34a526d9a5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_c8277e68-a926-43e4-8116-df6dc9c4c43c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bb77c6eb-0e6b-4187-a2a8-fc34a526d9a5" xlink:to="loc_us-gaap_AwardTypeAxis_c8277e68-a926-43e4-8116-df6dc9c4c43c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c8277e68-a926-43e4-8116-df6dc9c4c43c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_c8277e68-a926-43e4-8116-df6dc9c4c43c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c8277e68-a926-43e4-8116-df6dc9c4c43c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_34911e83-7f9c-4366-a730-0eb9d091c230" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_c8277e68-a926-43e4-8116-df6dc9c4c43c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_34911e83-7f9c-4366-a730-0eb9d091c230" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockCompensationPlanMember_c3718293-15a1-4b6a-a492-1fe0dd5bb886" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockCompensationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_34911e83-7f9c-4366-a730-0eb9d091c230" xlink:to="loc_us-gaap_StockCompensationPlanMember_c3718293-15a1-4b6a-a492-1fe0dd5bb886" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_99171161-00d9-41ed-a136-3ac939194ada" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_34911e83-7f9c-4366-a730-0eb9d091c230" xlink:to="loc_us-gaap_PerformanceSharesMember_99171161-00d9-41ed-a136-3ac939194ada" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_cc5af1cb-3674-44eb-aace-7b0afea29d9f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bb77c6eb-0e6b-4187-a2a8-fc34a526d9a5" xlink:to="loc_us-gaap_PlanNameAxis_cc5af1cb-3674-44eb-aace-7b0afea29d9f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_cc5af1cb-3674-44eb-aace-7b0afea29d9f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_cc5af1cb-3674-44eb-aace-7b0afea29d9f" xlink:to="loc_us-gaap_PlanNameDomain_cc5af1cb-3674-44eb-aace-7b0afea29d9f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_cea9e37b-fe84-48c1-82db-87a42bac9541" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_cc5af1cb-3674-44eb-aace-7b0afea29d9f" xlink:to="loc_us-gaap_PlanNameDomain_cea9e37b-fe84-48c1-82db-87a42bac9541" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OmnibusIncentivePlanMember_dfbc953a-5250-435f-90d6-b75999902196" xlink:href="gntx-20220630.xsd#gntx_OmnibusIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_cea9e37b-fe84-48c1-82db-87a42bac9541" xlink:to="loc_gntx_OmnibusIncentivePlanMember_dfbc953a-5250-435f-90d6-b75999902196" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_EmployeeStockOptionPlanMember_01e155f5-4769-45f3-bdd5-2f8456314ee0" xlink:href="gntx-20220630.xsd#gntx_EmployeeStockOptionPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_cea9e37b-fe84-48c1-82db-87a42bac9541" xlink:to="loc_gntx_EmployeeStockOptionPlanMember_01e155f5-4769-45f3-bdd5-2f8456314ee0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_RestrictedStockPlanMember_fcc50dac-20d5-45d5-b597-1f84c9696d35" xlink:href="gntx-20220630.xsd#gntx_RestrictedStockPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_cea9e37b-fe84-48c1-82db-87a42bac9541" xlink:to="loc_gntx_RestrictedStockPlanMember_fcc50dac-20d5-45d5-b597-1f84c9696d35" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_a4047e3d-4c52-42f2-9db3-67941e8e133a" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bb77c6eb-0e6b-4187-a2a8-fc34a526d9a5" xlink:to="loc_srt_RangeAxis_a4047e3d-4c52-42f2-9db3-67941e8e133a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_a4047e3d-4c52-42f2-9db3-67941e8e133a_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_a4047e3d-4c52-42f2-9db3-67941e8e133a" xlink:to="loc_srt_RangeMember_a4047e3d-4c52-42f2-9db3-67941e8e133a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_8b8ae658-1451-4998-864c-4c8ff4d680b0" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_a4047e3d-4c52-42f2-9db3-67941e8e133a" xlink:to="loc_srt_RangeMember_8b8ae658-1451-4998-864c-4c8ff4d680b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_d54d27af-78fa-4f08-a7cf-a668340e9b95" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_8b8ae658-1451-4998-864c-4c8ff4d680b0" xlink:to="loc_srt_MinimumMember_d54d27af-78fa-4f08-a7cf-a668340e9b95" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_8b039663-4de5-4280-96a3-6966a6395fa8" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_8b8ae658-1451-4998-864c-4c8ff4d680b0" xlink:to="loc_srt_MaximumMember_8b039663-4de5-4280-96a3-6966a6395fa8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_4d141f9d-ce4d-4470-a9de-47be77d4c37f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_bb77c6eb-0e6b-4187-a2a8-fc34a526d9a5" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_4d141f9d-ce4d-4470-a9de-47be77d4c37f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_4d141f9d-ce4d-4470-a9de-47be77d4c37f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_4d141f9d-ce4d-4470-a9de-47be77d4c37f" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_4d141f9d-ce4d-4470-a9de-47be77d4c37f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_e70fd97f-65ad-4903-a14d-036a1cf08bcf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_4d141f9d-ce4d-4470-a9de-47be77d4c37f" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_e70fd97f-65ad-4903-a14d-036a1cf08bcf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_cf292058-be5c-4f70-84ca-6ce776f029d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_e70fd97f-65ad-4903-a14d-036a1cf08bcf" xlink:to="loc_us-gaap_EmployeeStockMember_cf292058-be5c-4f70-84ca-6ce776f029d6" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlansSharesIssuedNetofSharesCanceledExpiredDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#StockBasedCompensationPlansSharesIssuedNetofSharesCanceledExpiredDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlansSharesIssuedNetofSharesCanceledExpiredDetails" xlink:type="extended" id="i514e7a58619743eb8d08897873f38e18_StockBasedCompensationPlansSharesIssuedNetofSharesCanceledExpiredDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e9b7eb1e-dd6b-444a-b88c-1591cb7b83f9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_0d9ab3dd-6cd6-4a69-8ec6-f2d2e38ae585" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e9b7eb1e-dd6b-444a-b88c-1591cb7b83f9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_0d9ab3dd-6cd6-4a69-8ec6-f2d2e38ae585" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_ac7ab7f9-6b6e-4bf0-bd95-017a47463ee8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e9b7eb1e-dd6b-444a-b88c-1591cb7b83f9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_ac7ab7f9-6b6e-4bf0-bd95-017a47463ee8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod_56c02973-b8c1-4ca2-bc26-2b20ee917f07" xlink:href="gntx-20220630.xsd#gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e9b7eb1e-dd6b-444a-b88c-1591cb7b83f9" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod_56c02973-b8c1-4ca2-bc26-2b20ee917f07" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsConversionRate_130b4e16-cbbe-46ff-a70f-aa3236c84a8d" xlink:href="gntx-20220630.xsd#gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsConversionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e9b7eb1e-dd6b-444a-b88c-1591cb7b83f9" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsConversionRate_130b4e16-cbbe-46ff-a70f-aa3236c84a8d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentConversionRate_e6424a41-21d7-41f1-9431-45063cbede17" xlink:href="gntx-20220630.xsd#gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentConversionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e9b7eb1e-dd6b-444a-b88c-1591cb7b83f9" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentConversionRate_e6424a41-21d7-41f1-9431-45063cbede17" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_d2af3a75-d4ae-4973-8b4d-920ffe33b022" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e9b7eb1e-dd6b-444a-b88c-1591cb7b83f9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_d2af3a75-d4ae-4973-8b4d-920ffe33b022" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3acd7bb8-0276-4431-a615-78fd03b55509" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_e9b7eb1e-dd6b-444a-b88c-1591cb7b83f9" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3acd7bb8-0276-4431-a615-78fd03b55509" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_f3194b90-d106-4963-911c-956cf78e93ba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3acd7bb8-0276-4431-a615-78fd03b55509" xlink:to="loc_us-gaap_AwardTypeAxis_f3194b90-d106-4963-911c-956cf78e93ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f3194b90-d106-4963-911c-956cf78e93ba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_f3194b90-d106-4963-911c-956cf78e93ba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f3194b90-d106-4963-911c-956cf78e93ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8bfe0b2a-712c-4bc2-a484-701a70283d0f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_f3194b90-d106-4963-911c-956cf78e93ba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8bfe0b2a-712c-4bc2-a484-701a70283d0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_NonQualifiedStockOptionMember_626f726d-15c3-494b-8bb4-9b002cf05638" xlink:href="gntx-20220630.xsd#gntx_NonQualifiedStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8bfe0b2a-712c-4bc2-a484-701a70283d0f" xlink:to="loc_gntx_NonQualifiedStockOptionMember_626f726d-15c3-494b-8bb4-9b002cf05638" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_7c648908-abf8-41a3-bd6b-fb8a376dd93d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8bfe0b2a-712c-4bc2-a484-701a70283d0f" xlink:to="loc_us-gaap_RestrictedStockMember_7c648908-abf8-41a3-bd6b-fb8a376dd93d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_4637e251-93bd-4979-a595-b01f9cf031b5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8bfe0b2a-712c-4bc2-a484-701a70283d0f" xlink:to="loc_us-gaap_PerformanceSharesMember_4637e251-93bd-4979-a595-b01f9cf031b5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_5abc17e5-aa19-4649-8ef9-ac1de3189a1d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3acd7bb8-0276-4431-a615-78fd03b55509" xlink:to="loc_us-gaap_PlanNameAxis_5abc17e5-aa19-4649-8ef9-ac1de3189a1d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_5abc17e5-aa19-4649-8ef9-ac1de3189a1d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_5abc17e5-aa19-4649-8ef9-ac1de3189a1d" xlink:to="loc_us-gaap_PlanNameDomain_5abc17e5-aa19-4649-8ef9-ac1de3189a1d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_99cde10c-e688-443e-9e2c-9f1854453262" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_5abc17e5-aa19-4649-8ef9-ac1de3189a1d" xlink:to="loc_us-gaap_PlanNameDomain_99cde10c-e688-443e-9e2c-9f1854453262" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OmnibusIncentivePlanMember_a0108fc9-90f0-4dcd-990b-48b5ce77aca1" xlink:href="gntx-20220630.xsd#gntx_OmnibusIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_99cde10c-e688-443e-9e2c-9f1854453262" xlink:to="loc_gntx_OmnibusIncentivePlanMember_a0108fc9-90f0-4dcd-990b-48b5ce77aca1" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncomeAOCIRollforwardDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#ComprehensiveIncomeAOCIRollforwardDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncomeAOCIRollforwardDetails" xlink:type="extended" id="i04dc3cb06fa849e09b2c7babf8362eb7_ComprehensiveIncomeAOCIRollforwardDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1aee127d-555f-45c3-9d01-2d74112153bb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_dd933d6c-96e3-44a7-9787-741a3d93b4c4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1aee127d-555f-45c3-9d01-2d74112153bb" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_dd933d6c-96e3-44a7-9787-741a3d93b4c4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_05b9b0aa-827d-42ad-8dee-97ea9adf8132" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_dd933d6c-96e3-44a7-9787-741a3d93b4c4" xlink:to="loc_us-gaap_StockholdersEquity_05b9b0aa-827d-42ad-8dee-97ea9adf8132" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_9a4117d2-24dc-41bd-9bbb-a346e947373d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_dd933d6c-96e3-44a7-9787-741a3d93b4c4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_9a4117d2-24dc-41bd-9bbb-a346e947373d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_aaded120-39b4-4d2a-a3c3-2b6f1fd2b37a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_dd933d6c-96e3-44a7-9787-741a3d93b4c4" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_aaded120-39b4-4d2a-a3c3-2b6f1fd2b37a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_19caa2ee-46a9-4333-8042-f94b67463cb2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_dd933d6c-96e3-44a7-9787-741a3d93b4c4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_19caa2ee-46a9-4333-8042-f94b67463cb2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_b1ab19c2-8f06-4871-a0b2-50a5ad7b30bc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_a63b2770-bd07-49c6-9af9-880fc7b2584c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1aee127d-555f-45c3-9d01-2d74112153bb" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_a63b2770-bd07-49c6-9af9-880fc7b2584c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_dd06d76a-4f3f-49d3-afbc-197819a1ede5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_1aee127d-555f-45c3-9d01-2d74112153bb" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_dd06d76a-4f3f-49d3-afbc-197819a1ede5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_3abf6368-badd-4982-ac29-8cf7e2861b1a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_dd06d76a-4f3f-49d3-afbc-197819a1ede5" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_3abf6368-badd-4982-ac29-8cf7e2861b1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_3abf6368-badd-4982-ac29-8cf7e2861b1a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_3abf6368-badd-4982-ac29-8cf7e2861b1a" xlink:to="loc_us-gaap_EquityComponentDomain_3abf6368-badd-4982-ac29-8cf7e2861b1a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_2addc8db-ac1d-4a17-bdc9-f82638292d0a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_3abf6368-badd-4982-ac29-8cf7e2861b1a" xlink:to="loc_us-gaap_EquityComponentDomain_2addc8db-ac1d-4a17-bdc9-f82638292d0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_619d3852-0624-403f-917f-b201807faeec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2addc8db-ac1d-4a17-bdc9-f82638292d0a" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_619d3852-0624-403f-917f-b201807faeec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_2703d9cd-6198-4292-828f-7e5e093dbaf3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_619d3852-0624-403f-917f-b201807faeec" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_2703d9cd-6198-4292-828f-7e5e093dbaf3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_b898a244-4eae-46a5-85f6-cc477c8dc695" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_619d3852-0624-403f-917f-b201807faeec" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_b898a244-4eae-46a5-85f6-cc477c8dc695" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncomeReclassificationOutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#ComprehensiveIncomeReclassificationOutofAccumulatedOtherComprehensiveIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncomeReclassificationOutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended" id="i8f5f7cb75e024dc1b29cf11547ca9dfb_ComprehensiveIncomeReclassificationOutofAccumulatedOtherComprehensiveIncomeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_7b21199b-6aec-421e-8006-06b8d6edd164" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiRealizedGainLoss_737d31b8-cfb7-4334-af67-7d51ebf4ad68" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquitySecuritiesFvNiRealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_7b21199b-6aec-421e-8006-06b8d6edd164" xlink:to="loc_us-gaap_EquitySecuritiesFvNiRealizedGainLoss_737d31b8-cfb7-4334-af67-7d51ebf4ad68" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_910804a2-8259-4409-a9bd-aca0d6ca6abd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_7b21199b-6aec-421e-8006-06b8d6edd164" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_910804a2-8259-4409-a9bd-aca0d6ca6abd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_845435e6-5de4-4d11-9879-581ec7b24f8d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_7b21199b-6aec-421e-8006-06b8d6edd164" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_845435e6-5de4-4d11-9879-581ec7b24f8d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_a52e8ed4-bfff-44c4-9c0e-c12cdd0b9ab8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_7b21199b-6aec-421e-8006-06b8d6edd164" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_a52e8ed4-bfff-44c4-9c0e-c12cdd0b9ab8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_5c75b682-8f6d-460e-a203-527c7c617d75" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_a52e8ed4-bfff-44c4-9c0e-c12cdd0b9ab8" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_5c75b682-8f6d-460e-a203-527c7c617d75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_5c75b682-8f6d-460e-a203-527c7c617d75_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_5c75b682-8f6d-460e-a203-527c7c617d75" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_5c75b682-8f6d-460e-a203-527c7c617d75_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_68640aea-134b-4ebd-a1ad-fd04c11f549c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_5c75b682-8f6d-460e-a203-527c7c617d75" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_68640aea-134b-4ebd-a1ad-fd04c11f549c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_6ba140ac-7ef2-4906-9510-5e1234488ec1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_68640aea-134b-4ebd-a1ad-fd04c11f549c" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_6ba140ac-7ef2-4906-9510-5e1234488ec1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_64cb63f0-8b53-4d8c-bda5-1b26c9e76d7f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_a52e8ed4-bfff-44c4-9c0e-c12cdd0b9ab8" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_64cb63f0-8b53-4d8c-bda5-1b26c9e76d7f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_64cb63f0-8b53-4d8c-bda5-1b26c9e76d7f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_64cb63f0-8b53-4d8c-bda5-1b26c9e76d7f" xlink:to="loc_us-gaap_EquityComponentDomain_64cb63f0-8b53-4d8c-bda5-1b26c9e76d7f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_cecfed14-bfce-42d8-9c01-9bd917157e80" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_64cb63f0-8b53-4d8c-bda5-1b26c9e76d7f" xlink:to="loc_us-gaap_EquityComponentDomain_cecfed14-bfce-42d8-9c01-9bd917157e80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_49a68ed4-e478-48c1-b860-a63cefe4fdb3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_cecfed14-bfce-42d8-9c01-9bd917157e80" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_49a68ed4-e478-48c1-b860-a63cefe4fdb3" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/DebtandFinancingArrangementsDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#DebtandFinancingArrangementsDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/DebtandFinancingArrangementsDetails" xlink:type="extended" id="i5473c462b9b44906bd3a53ecda611aea_DebtandFinancingArrangementsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_77d48343-a244-40ff-9d8f-42ec14160c79" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_b33331d4-3b38-4fa0-9bfd-f6450bbc85b0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_77d48343-a244-40ff-9d8f-42ec14160c79" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_b33331d4-3b38-4fa0-9bfd-f6450bbc85b0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount_f0a4afb3-1edc-41e1-9932-88782baea823" xlink:href="gntx-20220630.xsd#gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_77d48343-a244-40ff-9d8f-42ec14160c79" xlink:to="loc_gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount_f0a4afb3-1edc-41e1-9932-88782baea823" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_1753dac9-9395-4594-8d32-415955e635d4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_77d48343-a244-40ff-9d8f-42ec14160c79" xlink:to="loc_us-gaap_LongTermDebt_1753dac9-9395-4594-8d32-415955e635d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_ab055ad4-fec8-44fa-952f-a6bde7114fac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_77d48343-a244-40ff-9d8f-42ec14160c79" xlink:to="loc_us-gaap_DebtInstrumentTable_ab055ad4-fec8-44fa-952f-a6bde7114fac" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_08c14cc3-ce97-40bd-b79e-b1ebd1e0a2b4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ab055ad4-fec8-44fa-952f-a6bde7114fac" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_08c14cc3-ce97-40bd-b79e-b1ebd1e0a2b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_08c14cc3-ce97-40bd-b79e-b1ebd1e0a2b4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_08c14cc3-ce97-40bd-b79e-b1ebd1e0a2b4" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_08c14cc3-ce97-40bd-b79e-b1ebd1e0a2b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_d0fd6e18-3a84-40dc-8aec-307f1e306c0a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_08c14cc3-ce97-40bd-b79e-b1ebd1e0a2b4" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_d0fd6e18-3a84-40dc-8aec-307f1e306c0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_cdaa7a0e-9f22-4b5b-891e-c874d4659b9d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_d0fd6e18-3a84-40dc-8aec-307f1e306c0a" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_cdaa7a0e-9f22-4b5b-891e-c874d4659b9d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_777f635f-0dba-484d-9af4-f634ebcfe9db" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_d0fd6e18-3a84-40dc-8aec-307f1e306c0a" xlink:to="loc_us-gaap_LineOfCreditMember_777f635f-0dba-484d-9af4-f634ebcfe9db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_SwingLoansMember_6216ef75-c34c-40a5-8c43-8f7715dcb580" xlink:href="gntx-20220630.xsd#gntx_SwingLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_d0fd6e18-3a84-40dc-8aec-307f1e306c0a" xlink:to="loc_gntx_SwingLoansMember_6216ef75-c34c-40a5-8c43-8f7715dcb580" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_ee1bf0e6-bc76-44a7-85c2-f42965f2ca24" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_d0fd6e18-3a84-40dc-8aec-307f1e306c0a" xlink:to="loc_us-gaap_LetterOfCreditMember_ee1bf0e6-bc76-44a7-85c2-f42965f2ca24" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/SegmentReportingScheduleofAutomotiveandOtherSegmentReportingDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#SegmentReportingScheduleofAutomotiveandOtherSegmentReportingDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/SegmentReportingScheduleofAutomotiveandOtherSegmentReportingDetails" xlink:type="extended" id="ie09aa5ab852640f08bf30cf7fad3e150_SegmentReportingScheduleofAutomotiveandOtherSegmentReportingDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_195da208-d93c-4c67-85de-16cfcf08a706" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_770d18a7-1cf2-42f3-a802-c6d0f7b5208a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_195da208-d93c-4c67-85de-16cfcf08a706" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_770d18a7-1cf2-42f3-a802-c6d0f7b5208a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_80fbf804-ed1e-4a2f-a962-c8e13155074c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_195da208-d93c-4c67-85de-16cfcf08a706" xlink:to="loc_us-gaap_OperatingIncomeLoss_80fbf804-ed1e-4a2f-a962-c8e13155074c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_6452a559-6978-47d8-b6e7-6764282f530a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_195da208-d93c-4c67-85de-16cfcf08a706" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_6452a559-6978-47d8-b6e7-6764282f530a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_8ca072a3-90ca-4139-8243-7a85a93c18c9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_6452a559-6978-47d8-b6e7-6764282f530a" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_8ca072a3-90ca-4139-8243-7a85a93c18c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_8ca072a3-90ca-4139-8243-7a85a93c18c9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_8ca072a3-90ca-4139-8243-7a85a93c18c9" xlink:to="loc_us-gaap_SegmentDomain_8ca072a3-90ca-4139-8243-7a85a93c18c9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_852ada44-c289-4fc2-b2a6-2811e5812fae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_8ca072a3-90ca-4139-8243-7a85a93c18c9" xlink:to="loc_us-gaap_SegmentDomain_852ada44-c289-4fc2-b2a6-2811e5812fae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveProductsSegmentMember_f4fce551-328d-4551-8b3a-3b059dbf0bfa" xlink:href="gntx-20220630.xsd#gntx_AutomotiveProductsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_852ada44-c289-4fc2-b2a6-2811e5812fae" xlink:to="loc_gntx_AutomotiveProductsSegmentMember_f4fce551-328d-4551-8b3a-3b059dbf0bfa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllOtherSegmentsMember_018ba722-2e0c-4e96-8d27-66318ab26c89" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AllOtherSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_852ada44-c289-4fc2-b2a6-2811e5812fae" xlink:to="loc_us-gaap_AllOtherSegmentsMember_018ba722-2e0c-4e96-8d27-66318ab26c89" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/RevenueDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#RevenueDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/RevenueDetails" xlink:type="extended" id="i3590cc8e88e746599ef737a6598b92ab_RevenueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_d3aa2891-9d4f-42c2-96cd-260c85c1dbd9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_5f06c1b8-a0c5-4cb3-b91d-9079387bd78f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_d3aa2891-9d4f-42c2-96cd-260c85c1dbd9" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_5f06c1b8-a0c5-4cb3-b91d-9079387bd78f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_af53bcb4-989e-4ccd-890b-86b46dad8b05" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_d3aa2891-9d4f-42c2-96cd-260c85c1dbd9" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_af53bcb4-989e-4ccd-890b-86b46dad8b05" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_3d1364c4-6f12-4e00-a2ff-848571a0ea9d" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_af53bcb4-989e-4ccd-890b-86b46dad8b05" xlink:to="loc_srt_StatementGeographicalAxis_3d1364c4-6f12-4e00-a2ff-848571a0ea9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_3d1364c4-6f12-4e00-a2ff-848571a0ea9d_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_3d1364c4-6f12-4e00-a2ff-848571a0ea9d" xlink:to="loc_srt_SegmentGeographicalDomain_3d1364c4-6f12-4e00-a2ff-848571a0ea9d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_6d42eaf5-41c8-4810-a3b0-f4ab67e52750" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_3d1364c4-6f12-4e00-a2ff-848571a0ea9d" xlink:to="loc_srt_SegmentGeographicalDomain_6d42eaf5-41c8-4810-a3b0-f4ab67e52750" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_ce1b90d8-d836-43fa-9ba0-acb8109139bd" xlink:href="https://xbrl.sec.gov/country/2022/country-2022.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_6d42eaf5-41c8-4810-a3b0-f4ab67e52750" xlink:to="loc_country_US_ce1b90d8-d836-43fa-9ba0-acb8109139bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_DE_c3092ea3-0dd7-4766-9d32-3b59ee21a5b4" xlink:href="https://xbrl.sec.gov/country/2022/country-2022.xsd#country_DE"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_6d42eaf5-41c8-4810-a3b0-f4ab67e52750" xlink:to="loc_country_DE_c3092ea3-0dd7-4766-9d32-3b59ee21a5b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_JP_191185a2-71a7-4c05-80a7-bac153070e18" xlink:href="https://xbrl.sec.gov/country/2022/country-2022.xsd#country_JP"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_6d42eaf5-41c8-4810-a3b0-f4ab67e52750" xlink:to="loc_country_JP_191185a2-71a7-4c05-80a7-bac153070e18" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_MX_444fcffa-e6de-405c-8536-a1666b33afcc" xlink:href="https://xbrl.sec.gov/country/2022/country-2022.xsd#country_MX"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_6d42eaf5-41c8-4810-a3b0-f4ab67e52750" xlink:to="loc_country_MX_444fcffa-e6de-405c-8536-a1666b33afcc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OtherCountriesMember_223ba7fa-0a57-448f-8394-6228074f4e58" xlink:href="gntx-20220630.xsd#gntx_OtherCountriesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_6d42eaf5-41c8-4810-a3b0-f4ab67e52750" xlink:to="loc_gntx_OtherCountriesMember_223ba7fa-0a57-448f-8394-6228074f4e58" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_2a0fd22c-d700-4b0f-9ee4-0d417c93e4eb" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_af53bcb4-989e-4ccd-890b-86b46dad8b05" xlink:to="loc_srt_ProductOrServiceAxis_2a0fd22c-d700-4b0f-9ee4-0d417c93e4eb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_2a0fd22c-d700-4b0f-9ee4-0d417c93e4eb_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_2a0fd22c-d700-4b0f-9ee4-0d417c93e4eb" xlink:to="loc_srt_ProductsAndServicesDomain_2a0fd22c-d700-4b0f-9ee4-0d417c93e4eb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_a49f6408-bdd2-491f-aeb7-1afb02bedbc2" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_2a0fd22c-d700-4b0f-9ee4-0d417c93e4eb" xlink:to="loc_srt_ProductsAndServicesDomain_a49f6408-bdd2-491f-aeb7-1afb02bedbc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveProductsMember_a648cabb-9498-418b-99cd-22ddb10b04f9" xlink:href="gntx-20220630.xsd#gntx_AutomotiveProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_a49f6408-bdd2-491f-aeb7-1afb02bedbc2" xlink:to="loc_gntx_AutomotiveProductsMember_a648cabb-9498-418b-99cd-22ddb10b04f9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveMirrorsElectronicsMember_a3b51da0-7700-4bab-b27c-b101e6a87be9" xlink:href="gntx-20220630.xsd#gntx_AutomotiveMirrorsElectronicsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_AutomotiveProductsMember_a648cabb-9498-418b-99cd-22ddb10b04f9" xlink:to="loc_gntx_AutomotiveMirrorsElectronicsMember_a3b51da0-7700-4bab-b27c-b101e6a87be9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_HomeLinkModulesMember_d2303f7d-3acd-4547-805b-4b57123418a1" xlink:href="gntx-20220630.xsd#gntx_HomeLinkModulesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_AutomotiveProductsMember_a648cabb-9498-418b-99cd-22ddb10b04f9" xlink:to="loc_gntx_HomeLinkModulesMember_d2303f7d-3acd-4547-805b-4b57123418a1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OtherProductsMember_4cce6e1a-2824-4f57-ae2e-f34ef4f2ebd9" xlink:href="gntx-20220630.xsd#gntx_OtherProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_a49f6408-bdd2-491f-aeb7-1afb02bedbc2" xlink:to="loc_gntx_OtherProductsMember_4cce6e1a-2824-4f57-ae2e-f34ef4f2ebd9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_FireProtectionProductsMember_ec7a39e2-f10d-43c6-a454-0bd1d5f6b867" xlink:href="gntx-20220630.xsd#gntx_FireProtectionProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_OtherProductsMember_4cce6e1a-2824-4f57-ae2e-f34ef4f2ebd9" xlink:to="loc_gntx_FireProtectionProductsMember_ec7a39e2-f10d-43c6-a454-0bd1d5f6b867" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AerospaceProductsMember_3325baf9-30d1-45eb-890c-97b101aae731" xlink:href="gntx-20220630.xsd#gntx_AerospaceProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_OtherProductsMember_4cce6e1a-2824-4f57-ae2e-f34ef4f2ebd9" xlink:to="loc_gntx_AerospaceProductsMember_3325baf9-30d1-45eb-890c-97b101aae731" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_ff9e549c-f600-4afb-af8a-48340a4fb036" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_af53bcb4-989e-4ccd-890b-86b46dad8b05" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_ff9e549c-f600-4afb-af8a-48340a4fb036" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_ff9e549c-f600-4afb-af8a-48340a4fb036_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_ff9e549c-f600-4afb-af8a-48340a4fb036" xlink:to="loc_us-gaap_SegmentDomain_ff9e549c-f600-4afb-af8a-48340a4fb036_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_f194f358-e351-4341-af16-f7bb9572c35a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_ff9e549c-f600-4afb-af8a-48340a4fb036" xlink:to="loc_us-gaap_SegmentDomain_f194f358-e351-4341-af16-f7bb9572c35a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveSegmentMember_75dadabb-5c01-4f52-8752-27d9650074e0" xlink:href="gntx-20220630.xsd#gntx_AutomotiveSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f194f358-e351-4341-af16-f7bb9572c35a" xlink:to="loc_gntx_AutomotiveSegmentMember_75dadabb-5c01-4f52-8752-27d9650074e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OtherSegmentMember_ab944278-3b9d-4e21-950b-92575c3efd96" xlink:href="gntx-20220630.xsd#gntx_OtherSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_f194f358-e351-4341-af16-f7bb9572c35a" xlink:to="loc_gntx_OtherSegmentMember_ab944278-3b9d-4e21-950b-92575c3efd96" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/LeasesDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#LeasesDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/LeasesDetails" xlink:type="extended" id="i129297dec2c0472dbff6a215809bd79e_LeasesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_4a833f16-d4cb-4459-a33c-022785a93532" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeOperatingLeaseRemainingLeaseTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_4a833f16-d4cb-4459-a33c-022785a93532" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_f150c875-b071-4a27-85a7-467dbea0b49e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_f150c875-b071-4a27-85a7-467dbea0b49e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_d5f20874-fa38-4edd-9339-2c7675fe3536" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_d5f20874-fa38-4edd-9339-2c7675fe3536" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_42b6b35d-cf22-4078-bcc3-b289f2434f54" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_42b6b35d-cf22-4078-bcc3-b289f2434f54" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_f3b21fad-e162-452b-9aed-3cc9086396b9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_f3b21fad-e162-452b-9aed-3cc9086396b9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_d919ab49-62c4-4cdc-9949-0b8224ffb9bc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_d919ab49-62c4-4cdc-9949-0b8224ffb9bc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_4763a342-3eb1-444f-ace6-a2c5db226ff0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_4763a342-3eb1-444f-ace6-a2c5db226ff0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_977b986c-eda4-4f67-bc81-fa1ca8de86be" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_977b986c-eda4-4f67-bc81-fa1ca8de86be" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour_2b507f0c-f1f8-4179-a856-b2bf0dea3817" xlink:href="gntx-20220630.xsd#gntx_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_gntx_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour_2b507f0c-f1f8-4179-a856-b2bf0dea3817" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_d6e66500-482a-485c-83de-ee3fa24774e4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_d6e66500-482a-485c-83de-ee3fa24774e4" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_9a597f0a-81d1-4538-b4f9-11c5d881ef14" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_9a597f0a-81d1-4538-b4f9-11c5d881ef14" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_ea5a6c56-a414-4173-ac7b-5204a0ec7bc9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_OperatingLeaseLiability_ea5a6c56-a414-4173-ac7b-5204a0ec7bc9" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_559b95d6-9381-458c-8f7f-ba9f75e17555" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_559b95d6-9381-458c-8f7f-ba9f75e17555" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_a14fbc3a-1c3f-4716-a3f2-acd88ac9fbfd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_a14fbc3a-1c3f-4716-a3f2-acd88ac9fbfd" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_32dabe4e-c1e0-4d07-b031-782baa0fabe8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList_6ee43444-390f-4d31-8c0b-d69ce0329a6e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList_6ee43444-390f-4d31-8c0b-d69ce0329a6e" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList_145d4b43-1613-4463-b431-81d4692ba176" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList_145d4b43-1613-4463-b431-81d4692ba176" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_b727a34c-5bd2-4d39-9e56-86083523b9c0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_bf034254-547d-448b-b4ec-0ca2f599c926" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_b727a34c-5bd2-4d39-9e56-86083523b9c0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_28024e4a-7eb5-4de5-a8f2-54180718afe3" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_b727a34c-5bd2-4d39-9e56-86083523b9c0" xlink:to="loc_srt_RangeAxis_28024e4a-7eb5-4de5-a8f2-54180718afe3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_28024e4a-7eb5-4de5-a8f2-54180718afe3_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_28024e4a-7eb5-4de5-a8f2-54180718afe3" xlink:to="loc_srt_RangeMember_28024e4a-7eb5-4de5-a8f2-54180718afe3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_15a5b76d-9c7e-40d4-bc36-52034e2c0c84" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_28024e4a-7eb5-4de5-a8f2-54180718afe3" xlink:to="loc_srt_RangeMember_15a5b76d-9c7e-40d4-bc36-52034e2c0c84" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_a026fb8d-07de-49c1-9401-c76f533152fc" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_15a5b76d-9c7e-40d4-bc36-52034e2c0c84" xlink:to="loc_srt_MinimumMember_a026fb8d-07de-49c1-9401-c76f533152fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_3eb81302-570a-4823-a6a1-ea5c8bebbec7" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_15a5b76d-9c7e-40d4-bc36-52034e2c0c84" xlink:to="loc_srt_MaximumMember_3eb81302-570a-4823-a6a1-ea5c8bebbec7" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/AcquisitionDetails" xlink:type="simple" xlink:href="gntx-20220630.xsd#AcquisitionDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/AcquisitionDetails" xlink:type="extended" id="i5e740d9587de45bfb948f82dd499f955_AcquisitionDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_9d8e31c8-c668-432f-8f96-229b5ef3edc1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_4506eefc-f031-4aa9-9e33-509b3c4ceea9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_9d8e31c8-c668-432f-8f96-229b5ef3edc1" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_4506eefc-f031-4aa9-9e33-509b3c4ceea9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_317f4ffb-3a3e-4957-89f8-7019f28fba71" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_9d8e31c8-c668-432f-8f96-229b5ef3edc1" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_317f4ffb-3a3e-4957-89f8-7019f28fba71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a2b48182-deb2-444f-a5b4-377ba42d813f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_9d8e31c8-c668-432f-8f96-229b5ef3edc1" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a2b48182-deb2-444f-a5b4-377ba42d813f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_ffa5607d-d78d-40cb-82a7-2f89409798f3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a2b48182-deb2-444f-a5b4-377ba42d813f" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_ffa5607d-d78d-40cb-82a7-2f89409798f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ffa5607d-d78d-40cb-82a7-2f89409798f3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_ffa5607d-d78d-40cb-82a7-2f89409798f3" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ffa5607d-d78d-40cb-82a7-2f89409798f3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a7b03a26-c124-4a1d-912a-1ab97dbe7394" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_ffa5607d-d78d-40cb-82a7-2f89409798f3" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a7b03a26-c124-4a1d-912a-1ab97dbe7394" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_GuardianOpticalTechnologiesMember_b13be143-797b-43c1-bfbf-274a103e5fa3" xlink:href="gntx-20220630.xsd#gntx_GuardianOpticalTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a7b03a26-c124-4a1d-912a-1ab97dbe7394" xlink:to="loc_gntx_GuardianOpticalTechnologiesMember_b13be143-797b-43c1-bfbf-274a103e5fa3" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-roles-2022.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/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.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="0"/>
  </link:definitionLink>
</link:linkbase>
