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

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:f40a4fac-31e8-4a00-9bc0-1e185d0a8899,g:0a940f29-ee12-4f90-bbd9-bd45b7dec7f2-->
<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-20220930.xsd#UnauditedCondensedConsolidatedStatementsofShareholdersInvestment"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsofShareholdersInvestment" xlink:type="extended" id="i6aaca4ffd7ec45b9bad8b021d6f97fe2_UnauditedCondensedConsolidatedStatementsofShareholdersInvestment">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_0840519b-2564-4416-a2c0-24ce6418d74e" 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_79718988-69a4-4aca-a66a-dfc381278365" 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_0840519b-2564-4416-a2c0-24ce6418d74e" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_79718988-69a4-4aca-a66a-dfc381278365" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_75d4dd70-38ba-4842-9275-89a1fab7ab27" 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_79718988-69a4-4aca-a66a-dfc381278365" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_75d4dd70-38ba-4842-9275-89a1fab7ab27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_9b9f87e7-24ab-4ad1-abbe-fd3e57e6cd8a" 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_79718988-69a4-4aca-a66a-dfc381278365" xlink:to="loc_us-gaap_StockholdersEquity_9b9f87e7-24ab-4ad1-abbe-fd3e57e6cd8a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_58992051-da81-40ff-b9d5-04bd1733afea" 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_79718988-69a4-4aca-a66a-dfc381278365" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_58992051-da81-40ff-b9d5-04bd1733afea" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_69808c8a-f5e5-4852-92c5-01ad850ad49b" 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_79718988-69a4-4aca-a66a-dfc381278365" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_69808c8a-f5e5-4852-92c5-01ad850ad49b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_StockIssuedDuringPeriodSharesEquityInvestmentPurchase_3843bab4-d10e-46f7-84a3-5225320b0355" xlink:href="gntx-20220930.xsd#gntx_StockIssuedDuringPeriodSharesEquityInvestmentPurchase"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_79718988-69a4-4aca-a66a-dfc381278365" xlink:to="loc_gntx_StockIssuedDuringPeriodSharesEquityInvestmentPurchase_3843bab4-d10e-46f7-84a3-5225320b0355" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_StockIssuedDuringPeriodValueEquityInvestmentPurchase_e9268589-8ef8-439a-aa8c-19f2ae282e6d" xlink:href="gntx-20220930.xsd#gntx_StockIssuedDuringPeriodValueEquityInvestmentPurchase"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_79718988-69a4-4aca-a66a-dfc381278365" xlink:to="loc_gntx_StockIssuedDuringPeriodValueEquityInvestmentPurchase_e9268589-8ef8-439a-aa8c-19f2ae282e6d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_337573b3-17ee-441c-aff7-141594954b82" 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_79718988-69a4-4aca-a66a-dfc381278365" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_337573b3-17ee-441c-aff7-141594954b82" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_b7b7bcb7-3bbe-49c0-85b7-bfe5beffb4e9" 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_79718988-69a4-4aca-a66a-dfc381278365" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_b7b7bcb7-3bbe-49c0-85b7-bfe5beffb4e9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_4a71c82e-7c08-43fc-9cd0-aa7c6b36eff4" 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_79718988-69a4-4aca-a66a-dfc381278365" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_4a71c82e-7c08-43fc-9cd0-aa7c6b36eff4" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_db42b2bc-1eb4-4230-8ec1-03c9686f2558" 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_79718988-69a4-4aca-a66a-dfc381278365" xlink:to="loc_us-gaap_DividendsCommonStockCash_db42b2bc-1eb4-4230-8ec1-03c9686f2558" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_c648500b-9527-41e9-bdbd-dea1ae7a51b5" 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_79718988-69a4-4aca-a66a-dfc381278365" xlink:to="loc_us-gaap_NetIncomeLoss_c648500b-9527-41e9-bdbd-dea1ae7a51b5" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_c854648b-9338-421c-b655-2e7d1af43bd9" 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_79718988-69a4-4aca-a66a-dfc381278365" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_c854648b-9338-421c-b655-2e7d1af43bd9" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_b3de0b09-2f85-4813-a9f7-8439b95bb76f" 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_350a11ca-8ce4-4298-904a-831f81686d98" 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_e2d66a21-4d55-4146-a446-642bf6df4a45" 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_0840519b-2564-4416-a2c0-24ce6418d74e" xlink:to="loc_us-gaap_StatementTable_e2d66a21-4d55-4146-a446-642bf6df4a45" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_b8c87877-e14a-4af2-a339-8a06d937b106" 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_e2d66a21-4d55-4146-a446-642bf6df4a45" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_b8c87877-e14a-4af2-a339-8a06d937b106" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_b8c87877-e14a-4af2-a339-8a06d937b106_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_b8c87877-e14a-4af2-a339-8a06d937b106" xlink:to="loc_us-gaap_EquityComponentDomain_b8c87877-e14a-4af2-a339-8a06d937b106_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_1ef386ca-f6f3-48cb-8ca2-c101b2a6e8dc" 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_b8c87877-e14a-4af2-a339-8a06d937b106" xlink:to="loc_us-gaap_EquityComponentDomain_1ef386ca-f6f3-48cb-8ca2-c101b2a6e8dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_37438b39-c5c6-41f1-bc29-5b38a81e5a91" 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_1ef386ca-f6f3-48cb-8ca2-c101b2a6e8dc" xlink:to="loc_us-gaap_CommonStockMember_37438b39-c5c6-41f1-bc29-5b38a81e5a91" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_a18db2cf-f7b1-4e44-a1a4-3a63bb90488f" 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_1ef386ca-f6f3-48cb-8ca2-c101b2a6e8dc" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_a18db2cf-f7b1-4e44-a1a4-3a63bb90488f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_9038093b-34d2-48a8-ac35-79bfb1cafb92" 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_1ef386ca-f6f3-48cb-8ca2-c101b2a6e8dc" xlink:to="loc_us-gaap_RetainedEarningsMember_9038093b-34d2-48a8-ac35-79bfb1cafb92" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_186bbaa2-1ea4-4831-ad6b-e9a457036466" 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_1ef386ca-f6f3-48cb-8ca2-c101b2a6e8dc" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_186bbaa2-1ea4-4831-ad6b-e9a457036466" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#GoodwillandOtherIntangibleAssetsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="extended" id="i767b736e68814802813a41d6bd6fb615_GoodwillandOtherIntangibleAssetsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_cf973b27-0e52-4f83-92fa-8aaebb894272" 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_f01e6b67-0980-42c4-8af1-d305ace09b26" 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_cf973b27-0e52-4f83-92fa-8aaebb894272" xlink:to="loc_us-gaap_Goodwill_f01e6b67-0980-42c4-8af1-d305ace09b26" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAcquiredDuringPeriod_d0d9716d-de62-4af8-bcc2-8e5dc3633973" 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_cf973b27-0e52-4f83-92fa-8aaebb894272" xlink:to="loc_us-gaap_GoodwillAcquiredDuringPeriod_d0d9716d-de62-4af8-bcc2-8e5dc3633973" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_720ca675-e0ba-4048-b601-d2670500d555" 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_cf973b27-0e52-4f83-92fa-8aaebb894272" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_720ca675-e0ba-4048-b601-d2670500d555" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_ce0f55c5-48cd-4583-b69e-8ef7ad624696" 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_cf973b27-0e52-4f83-92fa-8aaebb894272" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_ce0f55c5-48cd-4583-b69e-8ef7ad624696" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_3e92ef11-57df-4c25-8d37-40629ddae36b" 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_cf973b27-0e52-4f83-92fa-8aaebb894272" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_3e92ef11-57df-4c25-8d37-40629ddae36b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_3cae85fa-c5b6-4ad6-a98b-fd06dc580a37" 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_cf973b27-0e52-4f83-92fa-8aaebb894272" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_3cae85fa-c5b6-4ad6-a98b-fd06dc580a37" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_de74fee0-8486-4c63-8d96-2de812ed7f7c" 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_cf973b27-0e52-4f83-92fa-8aaebb894272" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_de74fee0-8486-4c63-8d96-2de812ed7f7c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_dd9a5c62-9aba-4135-93ee-5a91d9087f80" 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_cf973b27-0e52-4f83-92fa-8aaebb894272" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_dd9a5c62-9aba-4135-93ee-5a91d9087f80" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_3bc13def-b40b-40cc-8ea0-90099cbb02c4" 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_cf973b27-0e52-4f83-92fa-8aaebb894272" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_3bc13def-b40b-40cc-8ea0-90099cbb02c4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_f17cacec-78d3-423e-bc90-5c02f51cb07b" 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_3bc13def-b40b-40cc-8ea0-90099cbb02c4" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_f17cacec-78d3-423e-bc90-5c02f51cb07b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f17cacec-78d3-423e-bc90-5c02f51cb07b_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_f17cacec-78d3-423e-bc90-5c02f51cb07b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f17cacec-78d3-423e-bc90-5c02f51cb07b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0f4f33da-cdee-4199-9855-511ec07c0ca2" 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_f17cacec-78d3-423e-bc90-5c02f51cb07b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0f4f33da-cdee-4199-9855-511ec07c0ca2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_HomeLinkMember_7695c639-2ec6-433b-b4c4-072bb4b80d7c" xlink:href="gntx-20220930.xsd#gntx_HomeLinkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0f4f33da-cdee-4199-9855-511ec07c0ca2" xlink:to="loc_gntx_HomeLinkMember_7695c639-2ec6-433b-b4c4-072bb4b80d7c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_VaporsensIncMember_c74864da-90be-4b38-8163-6fab49e3087a" xlink:href="gntx-20220930.xsd#gntx_VaporsensIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0f4f33da-cdee-4199-9855-511ec07c0ca2" xlink:to="loc_gntx_VaporsensIncMember_c74864da-90be-4b38-8163-6fab49e3087a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AirCraftGlassMember_ea6f01e2-60b7-4cd4-87df-f49bc948e245" xlink:href="gntx-20220930.xsd#gntx_AirCraftGlassMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0f4f33da-cdee-4199-9855-511ec07c0ca2" xlink:to="loc_gntx_AirCraftGlassMember_ea6f01e2-60b7-4cd4-87df-f49bc948e245" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ArgilIncMember_22144cd2-6d6d-4f90-a179-acf42c84cac4" xlink:href="gntx-20220930.xsd#gntx_ArgilIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0f4f33da-cdee-4199-9855-511ec07c0ca2" xlink:to="loc_gntx_ArgilIncMember_22144cd2-6d6d-4f90-a179-acf42c84cac4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_GuardianOpticalTechnologiesMember_39297134-c612-4326-9049-a0a516cb7dba" xlink:href="gntx-20220930.xsd#gntx_GuardianOpticalTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0f4f33da-cdee-4199-9855-511ec07c0ca2" xlink:to="loc_gntx_GuardianOpticalTechnologiesMember_39297134-c612-4326-9049-a0a516cb7dba" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails" xlink:type="extended" id="idc042ec066d543b79570892ace3da92b_GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_0f1d4848-4e0b-4055-9b05-87e6ec642e85" 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_30bcadc8-0784-4817-a87b-43519782c6a5" 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_0f1d4848-4e0b-4055-9b05-87e6ec642e85" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_30bcadc8-0784-4817-a87b-43519782c6a5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_52fcff21-2c28-45be-b2ef-f1ba399e8e0a" 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_0f1d4848-4e0b-4055-9b05-87e6ec642e85" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_52fcff21-2c28-45be-b2ef-f1ba399e8e0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_36e0ea98-3d95-48e8-b89c-3b304ed74ab4" 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_0f1d4848-4e0b-4055-9b05-87e6ec642e85" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_36e0ea98-3d95-48e8-b89c-3b304ed74ab4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_65e003a6-e643-4299-99da-0849181c0f74" 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_0f1d4848-4e0b-4055-9b05-87e6ec642e85" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_65e003a6-e643-4299-99da-0849181c0f74" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_c1990903-6e64-494d-bca5-1ad94aaf9ca3" 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_0f1d4848-4e0b-4055-9b05-87e6ec642e85" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_c1990903-6e64-494d-bca5-1ad94aaf9ca3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_ce9f35f6-3a53-4d24-9b11-702163c0e21c" 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_0f1d4848-4e0b-4055-9b05-87e6ec642e85" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_ce9f35f6-3a53-4d24-9b11-702163c0e21c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_IntangiblePatentsAndAssetsGrossExcludingGoodwill_559c0516-7838-4360-9419-b4f6c78067c3" xlink:href="gntx-20220930.xsd#gntx_IntangiblePatentsAndAssetsGrossExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_0f1d4848-4e0b-4055-9b05-87e6ec642e85" xlink:to="loc_gntx_IntangiblePatentsAndAssetsGrossExcludingGoodwill_559c0516-7838-4360-9419-b4f6c78067c3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_FiniteLivedIntangiblePatentsAndAssetsAccumulatedAmortization_2c95014f-39ec-4c02-a5ef-d5e0b7865a33" xlink:href="gntx-20220930.xsd#gntx_FiniteLivedIntangiblePatentsAndAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_0f1d4848-4e0b-4055-9b05-87e6ec642e85" xlink:to="loc_gntx_FiniteLivedIntangiblePatentsAndAssetsAccumulatedAmortization_2c95014f-39ec-4c02-a5ef-d5e0b7865a33" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_IntangiblePatentsAndAssetsNetExcludingGoodwill_d4bd101b-f4fa-4098-998d-9c673f76a625" xlink:href="gntx-20220930.xsd#gntx_IntangiblePatentsAndAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_0f1d4848-4e0b-4055-9b05-87e6ec642e85" xlink:to="loc_gntx_IntangiblePatentsAndAssetsNetExcludingGoodwill_d4bd101b-f4fa-4098-998d-9c673f76a625" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_42228143-3235-4f35-a698-ce825504c017" 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_0f1d4848-4e0b-4055-9b05-87e6ec642e85" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_42228143-3235-4f35-a698-ce825504c017" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_c07d2312-0852-43d5-a353-d3cc40bfaf51" 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_0f1d4848-4e0b-4055-9b05-87e6ec642e85" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_c07d2312-0852-43d5-a353-d3cc40bfaf51" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_34b03851-b962-46dc-9325-d39281feb459" 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_c07d2312-0852-43d5-a353-d3cc40bfaf51" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_34b03851-b962-46dc-9325-d39281feb459" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_34b03851-b962-46dc-9325-d39281feb459_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_34b03851-b962-46dc-9325-d39281feb459" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_34b03851-b962-46dc-9325-d39281feb459_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_9b90940d-764e-45ef-9553-9371c9142565" 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_34b03851-b962-46dc-9325-d39281feb459" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_9b90940d-764e-45ef-9553-9371c9142565" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_09f6d88c-092b-4443-aa06-23bee0909ff8" 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_9b90940d-764e-45ef-9553-9371c9142565" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_09f6d88c-092b-4443-aa06-23bee0909ff8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LicensingAgreementsMember_f518ccd1-3b48-4110-aa18-de8ea33147b1" 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_9b90940d-764e-45ef-9553-9371c9142565" xlink:to="loc_us-gaap_LicensingAgreementsMember_f518ccd1-3b48-4110-aa18-de8ea33147b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InProcessResearchAndDevelopmentMember_7485c5d2-e2a8-4a4e-b8bd-b1a9459cac51" 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_9b90940d-764e-45ef-9553-9371c9142565" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_7485c5d2-e2a8-4a4e-b8bd-b1a9459cac51" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e27696d4-9f70-456d-84fb-af41c01ae469" 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_c07d2312-0852-43d5-a353-d3cc40bfaf51" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_e27696d4-9f70-456d-84fb-af41c01ae469" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e27696d4-9f70-456d-84fb-af41c01ae469_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_e27696d4-9f70-456d-84fb-af41c01ae469" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_e27696d4-9f70-456d-84fb-af41c01ae469_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d17365a3-2636-421d-aecd-8bd2d7358c2e" 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_e27696d4-9f70-456d-84fb-af41c01ae469" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d17365a3-2636-421d-aecd-8bd2d7358c2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentsMember_32456b33-7aa8-41e8-b64f-a77020d56282" 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_d17365a3-2636-421d-aecd-8bd2d7358c2e" xlink:to="loc_us-gaap_PatentsMember_32456b33-7aa8-41e8-b64f-a77020d56282" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_cd68e0ea-829e-42dc-8f97-cd22a7d86ae1" 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_d17365a3-2636-421d-aecd-8bd2d7358c2e" xlink:to="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_cd68e0ea-829e-42dc-8f97-cd22a7d86ae1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_97b04732-5fcb-4b53-9ce7-1accb62268e4" 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_d17365a3-2636-421d-aecd-8bd2d7358c2e" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_97b04732-5fcb-4b53-9ce7-1accb62268e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerContractsMember_6c7c1be4-46d6-4187-a486-bbe4b69bd621" 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_d17365a3-2636-421d-aecd-8bd2d7358c2e" xlink:to="loc_us-gaap_CustomerContractsMember_6c7c1be4-46d6-4187-a486-bbe4b69bd621" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_b7e737c7-5430-478f-afa8-feff1131caf1" 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_d17365a3-2636-421d-aecd-8bd2d7358c2e" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_b7e737c7-5430-478f-afa8-feff1131caf1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_PatentsAndOtherIntangibleAssetsMember_468d7c3a-018f-4236-b5ff-856a7c17e8a7" xlink:href="gntx-20220930.xsd#gntx_PatentsAndOtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d17365a3-2636-421d-aecd-8bd2d7358c2e" xlink:to="loc_gntx_PatentsAndOtherIntangibleAssetsMember_468d7c3a-018f-4236-b5ff-856a7c17e8a7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_e1b7eab5-88da-4476-85fd-d6a37b3dcc0d" 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_c07d2312-0852-43d5-a353-d3cc40bfaf51" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_e1b7eab5-88da-4476-85fd-d6a37b3dcc0d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_e1b7eab5-88da-4476-85fd-d6a37b3dcc0d_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_e1b7eab5-88da-4476-85fd-d6a37b3dcc0d" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_e1b7eab5-88da-4476-85fd-d6a37b3dcc0d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d6867a3d-b3dc-425a-9d25-3b0b240c507b" 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_e1b7eab5-88da-4476-85fd-d6a37b3dcc0d" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d6867a3d-b3dc-425a-9d25-3b0b240c507b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_VaporsensIncMember_515e52ab-6dc8-4272-8389-05b08af07495" xlink:href="gntx-20220930.xsd#gntx_VaporsensIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d6867a3d-b3dc-425a-9d25-3b0b240c507b" xlink:to="loc_gntx_VaporsensIncMember_515e52ab-6dc8-4272-8389-05b08af07495" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ArgilIncMember_c301910f-85d5-42af-ae45-dc891c4d69ae" xlink:href="gntx-20220930.xsd#gntx_ArgilIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d6867a3d-b3dc-425a-9d25-3b0b240c507b" xlink:to="loc_gntx_ArgilIncMember_c301910f-85d5-42af-ae45-dc891c4d69ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AirCraftGlassMember_3cd5631e-133c-4052-83ec-570d2c8e511b" xlink:href="gntx-20220930.xsd#gntx_AirCraftGlassMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d6867a3d-b3dc-425a-9d25-3b0b240c507b" xlink:to="loc_gntx_AirCraftGlassMember_3cd5631e-133c-4052-83ec-570d2c8e511b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_GuardianOpticalTechnologiesMember_9126dd01-f82f-40c1-b919-ba426195cbb9" xlink:href="gntx-20220930.xsd#gntx_GuardianOpticalTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d6867a3d-b3dc-425a-9d25-3b0b240c507b" xlink:to="loc_gntx_GuardianOpticalTechnologiesMember_9126dd01-f82f-40c1-b919-ba426195cbb9" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsNarrativeDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#InvestmentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsNarrativeDetails" xlink:type="extended" id="icc7538ae8044448980050163de575877_InvestmentsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_68121a02-e67e-425b-adc6-fb8e574f5e48" 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_5b72b6aa-c622-430c-bc4a-1ac7bee67b16" 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_68121a02-e67e-425b-adc6-fb8e574f5e48" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_5b72b6aa-c622-430c-bc4a-1ac7bee67b16" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_12d4fc74-29d4-47b8-9cad-0aa37f47bcb0" 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_68121a02-e67e-425b-adc6-fb8e574f5e48" xlink:to="loc_us-gaap_EquityMethodInvestments_12d4fc74-29d4-47b8-9cad-0aa37f47bcb0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_6390067f-fa23-4348-ba70-55f6def8b5dd" 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_68121a02-e67e-425b-adc6-fb8e574f5e48" xlink:to="loc_us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_6390067f-fa23-4348-ba70-55f6def8b5dd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_4df040c2-619c-4c56-9f2e-4f4b981685b9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsToAcquireEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_68121a02-e67e-425b-adc6-fb8e574f5e48" xlink:to="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_4df040c2-619c-4c56-9f2e-4f4b981685b9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_fb5588bb-f087-4843-bd91-6af886333894" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_68121a02-e67e-425b-adc6-fb8e574f5e48" xlink:to="loc_us-gaap_CommonStockValue_fb5588bb-f087-4843-bd91-6af886333894" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestments_030ad26d-19b8-422a-8356-134eab2686ac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_68121a02-e67e-425b-adc6-fb8e574f5e48" xlink:to="loc_us-gaap_ShortTermInvestments_030ad26d-19b8-422a-8356-134eab2686ac" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermInvestments_b75f6dd9-2ae0-4a12-8612-11c8ac89cea8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_68121a02-e67e-425b-adc6-fb8e574f5e48" xlink:to="loc_us-gaap_LongTermInvestments_b75f6dd9-2ae0-4a12-8612-11c8ac89cea8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_121979e3-7fc9-40a6-8f82-2d75ddafa78d" 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_68121a02-e67e-425b-adc6-fb8e574f5e48" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_121979e3-7fc9-40a6-8f82-2d75ddafa78d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_6fa4a411-41b0-426b-a325-52afddebc703" 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_121979e3-7fc9-40a6-8f82-2d75ddafa78d" xlink:to="loc_srt_RangeAxis_6fa4a411-41b0-426b-a325-52afddebc703" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_6fa4a411-41b0-426b-a325-52afddebc703_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_6fa4a411-41b0-426b-a325-52afddebc703" xlink:to="loc_srt_RangeMember_6fa4a411-41b0-426b-a325-52afddebc703_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_44cf32d4-bdf2-4383-8ae3-a8f669b86780" 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_6fa4a411-41b0-426b-a325-52afddebc703" xlink:to="loc_srt_RangeMember_44cf32d4-bdf2-4383-8ae3-a8f669b86780" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_b314ab06-6a22-41f9-a308-c6cd4867643e" 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_44cf32d4-bdf2-4383-8ae3-a8f669b86780" xlink:to="loc_srt_MinimumMember_b314ab06-6a22-41f9-a308-c6cd4867643e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_5fc9a1c4-b3ef-4536-a5aa-ef420ba368af" 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_44cf32d4-bdf2-4383-8ae3-a8f669b86780" xlink:to="loc_srt_MaximumMember_5fc9a1c4-b3ef-4536-a5aa-ef420ba368af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_54cabda5-e9f2-40d4-aa06-502f3e2f3ec0" 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_121979e3-7fc9-40a6-8f82-2d75ddafa78d" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_54cabda5-e9f2-40d4-aa06-502f3e2f3ec0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_54cabda5-e9f2-40d4-aa06-502f3e2f3ec0_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_54cabda5-e9f2-40d4-aa06-502f3e2f3ec0" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_54cabda5-e9f2-40d4-aa06-502f3e2f3ec0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_baa2ff38-86cc-477b-aa51-f4f4cf2edb80" 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_54cabda5-e9f2-40d4-aa06-502f3e2f3ec0" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_baa2ff38-86cc-477b-aa51-f4f4cf2edb80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_6692e166-03ad-40dd-a152-ef225dab9db7" 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_BalanceSheetLocationDomain_baa2ff38-86cc-477b-aa51-f4f4cf2edb80" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_6692e166-03ad-40dd-a152-ef225dab9db7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_LongTermInvestmentsMember_b79bac37-5907-44e1-b86b-091663bf50eb" xlink:href="gntx-20220930.xsd#gntx_LongTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_baa2ff38-86cc-477b-aa51-f4f4cf2edb80" xlink:to="loc_gntx_LongTermInvestmentsMember_b79bac37-5907-44e1-b86b-091663bf50eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_636b83c7-af5b-4ae9-a695-71ee0592f97c" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_121979e3-7fc9-40a6-8f82-2d75ddafa78d" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_636b83c7-af5b-4ae9-a695-71ee0592f97c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_636b83c7-af5b-4ae9-a695-71ee0592f97c_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_636b83c7-af5b-4ae9-a695-71ee0592f97c" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_636b83c7-af5b-4ae9-a695-71ee0592f97c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_221edd8e-5c45-4950-857d-3606db372e1f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_636b83c7-af5b-4ae9-a695-71ee0592f97c" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_221edd8e-5c45-4950-857d-3606db372e1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_GentexCorporationMember_b6594a70-71dc-498e-8526-d2765ace6a07" xlink:href="gntx-20220930.xsd#gntx_GentexCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_221edd8e-5c45-4950-857d-3606db372e1f" xlink:to="loc_gntx_GentexCorporationMember_b6594a70-71dc-498e-8526-d2765ace6a07" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_GreenMarblesMember_ea0193d1-0d75-4e1f-b68a-4f6f727a410c" xlink:href="gntx-20220930.xsd#gntx_GreenMarblesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_221edd8e-5c45-4950-857d-3606db372e1f" xlink:to="loc_gntx_GreenMarblesMember_ea0193d1-0d75-4e1f-b68a-4f6f727a410c" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails" xlink:type="extended" id="ia88fb6d4b4ed4003a592f69cd229ec22_InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_71f188d3-8686-4ba4-989b-74eeb7fbfef0" 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_d8b8b25a-4eff-47f0-9e9b-e3019ba7bcab" 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_71f188d3-8686-4ba4-989b-74eeb7fbfef0" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_d8b8b25a-4eff-47f0-9e9b-e3019ba7bcab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_47df7fec-b54a-40b9-8b3c-5b64c2b577d8" 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_71f188d3-8686-4ba4-989b-74eeb7fbfef0" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_47df7fec-b54a-40b9-8b3c-5b64c2b577d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_0741c54a-c821-407b-b096-52db32214639" 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_71f188d3-8686-4ba4-989b-74eeb7fbfef0" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_0741c54a-c821-407b-b096-52db32214639" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_549d68c1-e6c1-4d5e-adf8-cb2440cb2493" 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_71f188d3-8686-4ba4-989b-74eeb7fbfef0" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_549d68c1-e6c1-4d5e-adf8-cb2440cb2493" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_dc5bf1d7-289f-45de-8a20-dc142309e3fa" 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_549d68c1-e6c1-4d5e-adf8-cb2440cb2493" xlink:to="loc_us-gaap_InvestmentTypeAxis_dc5bf1d7-289f-45de-8a20-dc142309e3fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_dc5bf1d7-289f-45de-8a20-dc142309e3fa_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_dc5bf1d7-289f-45de-8a20-dc142309e3fa" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_dc5bf1d7-289f-45de-8a20-dc142309e3fa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_fa3b1d8e-049c-4157-bd57-008d3782581a" 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_dc5bf1d7-289f-45de-8a20-dc142309e3fa" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_fa3b1d8e-049c-4157-bd57-008d3782581a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_f69b1c0d-2c50-4540-a121-074944d33b10" 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_fa3b1d8e-049c-4157-bd57-008d3782581a" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_f69b1c0d-2c50-4540-a121-074944d33b10" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermInvestmentsMember_e6781727-77a0-419d-8994-75a88c69134a" 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_fa3b1d8e-049c-4157-bd57-008d3782581a" xlink:to="loc_us-gaap_OtherLongTermInvestmentsMember_e6781727-77a0-419d-8994-75a88c69134a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_e1cdf031-fdb0-42b7-a80c-bd5a81d17204" 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_549d68c1-e6c1-4d5e-adf8-cb2440cb2493" xlink:to="loc_us-gaap_FinancialInstrumentAxis_e1cdf031-fdb0-42b7-a80c-bd5a81d17204" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e1cdf031-fdb0-42b7-a80c-bd5a81d17204_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_e1cdf031-fdb0-42b7-a80c-bd5a81d17204" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e1cdf031-fdb0-42b7-a80c-bd5a81d17204_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_df5f1b0f-067d-4ed4-8821-74edab3ecf8a" 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_e1cdf031-fdb0-42b7-a80c-bd5a81d17204" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_df5f1b0f-067d-4ed4-8821-74edab3ecf8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_999e5332-dfa6-44be-95cd-129e84dc4c99" 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_df5f1b0f-067d-4ed4-8821-74edab3ecf8a" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_999e5332-dfa6-44be-95cd-129e84dc4c99" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_c28cccb8-b035-46ac-a02a-3d64eaeff13c" 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_df5f1b0f-067d-4ed4-8821-74edab3ecf8a" xlink:to="loc_us-gaap_CertificatesOfDepositMember_c28cccb8-b035-46ac-a02a-3d64eaeff13c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_6dfbb432-83c0-43c5-908d-94a4ad51622b" 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_df5f1b0f-067d-4ed4-8821-74edab3ecf8a" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_6dfbb432-83c0-43c5-908d-94a4ad51622b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_d14064d9-64b0-44e7-bf8e-8d64497de309" 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_df5f1b0f-067d-4ed4-8821-74edab3ecf8a" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_d14064d9-64b0-44e7-bf8e-8d64497de309" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MunicipalBondsMember_56ce3f82-93ec-469a-bc46-9ee534ed190a" 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_df5f1b0f-067d-4ed4-8821-74edab3ecf8a" xlink:to="loc_us-gaap_MunicipalBondsMember_56ce3f82-93ec-469a-bc46-9ee534ed190a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_7b393562-0406-4232-ae21-80e15b106ce8" 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_df5f1b0f-067d-4ed4-8821-74edab3ecf8a" xlink:to="loc_us-gaap_OtherDebtSecuritiesMember_7b393562-0406-4232-ae21-80e15b106ce8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_997c05b5-edc0-44cd-8225-a48d02091b0c" 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_549d68c1-e6c1-4d5e-adf8-cb2440cb2493" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_997c05b5-edc0-44cd-8225-a48d02091b0c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_997c05b5-edc0-44cd-8225-a48d02091b0c_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_997c05b5-edc0-44cd-8225-a48d02091b0c" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_997c05b5-edc0-44cd-8225-a48d02091b0c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_46060352-cf4d-43ed-a757-8aaa8af99ec2" 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_997c05b5-edc0-44cd-8225-a48d02091b0c" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_46060352-cf4d-43ed-a757-8aaa8af99ec2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_935b8f01-9a70-4b4e-97b0-827b893608a1" 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_46060352-cf4d-43ed-a757-8aaa8af99ec2" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_935b8f01-9a70-4b4e-97b0-827b893608a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_4c2bf57d-1f82-427a-8cb3-fba53cb6cd96" 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_46060352-cf4d-43ed-a757-8aaa8af99ec2" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_4c2bf57d-1f82-427a-8cb3-fba53cb6cd96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_2f6ce814-25aa-48ed-95d5-44341e42ce89" 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_46060352-cf4d-43ed-a757-8aaa8af99ec2" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_2f6ce814-25aa-48ed-95d5-44341e42ce89" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails" xlink:type="extended" id="i8a026bef350a42bab4bf17fdecffa633_InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_93f9a0eb-f3ec-4f8c-a95c-615c26138742" 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_AvailableForSaleDebtSecuritiesAmortizedCostBasis_d90ee431-6319-4e3e-91b9-792bb4156bda" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_93f9a0eb-f3ec-4f8c-a95c-615c26138742" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_d90ee431-6319-4e3e-91b9-792bb4156bda" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_eaac4f27-970c-4457-8699-08484cf4ec8f" 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_93f9a0eb-f3ec-4f8c-a95c-615c26138742" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_eaac4f27-970c-4457-8699-08484cf4ec8f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_164d8adb-b09c-43cf-8742-0fc55a1a63c4" 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_93f9a0eb-f3ec-4f8c-a95c-615c26138742" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_164d8adb-b09c-43cf-8742-0fc55a1a63c4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_daf85b0d-a9aa-4214-a088-ef51b64d3974" 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_93f9a0eb-f3ec-4f8c-a95c-615c26138742" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_daf85b0d-a9aa-4214-a088-ef51b64d3974" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1c8fb375-eca7-4698-aa1c-c1c89490f307" 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_93f9a0eb-f3ec-4f8c-a95c-615c26138742" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1c8fb375-eca7-4698-aa1c-c1c89490f307" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_InvestmentLengthAxis_0ed550cf-7a40-4aae-8a64-ee43cee1ff98" xlink:href="gntx-20220930.xsd#gntx_InvestmentLengthAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1c8fb375-eca7-4698-aa1c-c1c89490f307" xlink:to="loc_gntx_InvestmentLengthAxis_0ed550cf-7a40-4aae-8a64-ee43cee1ff98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_InvestmentLengthDomain_0ed550cf-7a40-4aae-8a64-ee43cee1ff98_default" xlink:href="gntx-20220930.xsd#gntx_InvestmentLengthDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_gntx_InvestmentLengthAxis_0ed550cf-7a40-4aae-8a64-ee43cee1ff98" xlink:to="loc_gntx_InvestmentLengthDomain_0ed550cf-7a40-4aae-8a64-ee43cee1ff98_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_InvestmentLengthDomain_4c8cdca2-9f66-438b-a154-5ba28a6500d6" xlink:href="gntx-20220930.xsd#gntx_InvestmentLengthDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_gntx_InvestmentLengthAxis_0ed550cf-7a40-4aae-8a64-ee43cee1ff98" xlink:to="loc_gntx_InvestmentLengthDomain_4c8cdca2-9f66-438b-a154-5ba28a6500d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_badc14ff-0c54-4a79-8245-7e64fcd55fab" 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_gntx_InvestmentLengthDomain_4c8cdca2-9f66-438b-a154-5ba28a6500d6" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_badc14ff-0c54-4a79-8245-7e64fcd55fab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermInvestmentsMember_c319706e-12a4-41f0-a940-903c748fd80c" 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_gntx_InvestmentLengthDomain_4c8cdca2-9f66-438b-a154-5ba28a6500d6" xlink:to="loc_us-gaap_OtherLongTermInvestmentsMember_c319706e-12a4-41f0-a940-903c748fd80c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_e4405318-b054-4715-91be-69b53d35c174" 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_1c8fb375-eca7-4698-aa1c-c1c89490f307" xlink:to="loc_us-gaap_FinancialInstrumentAxis_e4405318-b054-4715-91be-69b53d35c174" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e4405318-b054-4715-91be-69b53d35c174_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_e4405318-b054-4715-91be-69b53d35c174" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e4405318-b054-4715-91be-69b53d35c174_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a78ee0f7-0eee-4bab-90ab-21eefe06bf94" 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_e4405318-b054-4715-91be-69b53d35c174" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a78ee0f7-0eee-4bab-90ab-21eefe06bf94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_76d49d10-846e-46cb-821c-855dfc59edf8" 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_a78ee0f7-0eee-4bab-90ab-21eefe06bf94" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_76d49d10-846e-46cb-821c-855dfc59edf8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_13d5d535-ab32-454e-8a01-25fa077c4a1f" 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_a78ee0f7-0eee-4bab-90ab-21eefe06bf94" xlink:to="loc_us-gaap_CertificatesOfDepositMember_13d5d535-ab32-454e-8a01-25fa077c4a1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_05d847de-6c09-4719-810d-782a72839405" 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_a78ee0f7-0eee-4bab-90ab-21eefe06bf94" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_05d847de-6c09-4719-810d-782a72839405" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_9cacb37a-cacc-4bac-8309-1e981a401204" 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_a78ee0f7-0eee-4bab-90ab-21eefe06bf94" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_9cacb37a-cacc-4bac-8309-1e981a401204" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MunicipalBondsMember_266aeaca-e4f4-4af8-a738-566eed38d006" 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_a78ee0f7-0eee-4bab-90ab-21eefe06bf94" xlink:to="loc_us-gaap_MunicipalBondsMember_266aeaca-e4f4-4af8-a738-566eed38d006" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_92dc4a09-cb20-41da-8ec5-e9fbbeeadeaf" 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_a78ee0f7-0eee-4bab-90ab-21eefe06bf94" xlink:to="loc_us-gaap_OtherDebtSecuritiesMember_92dc4a09-cb20-41da-8ec5-e9fbbeeadeaf" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsInvestmentsClassifiedbyContractualMaturityDateDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#InvestmentsInvestmentsClassifiedbyContractualMaturityDateDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsInvestmentsClassifiedbyContractualMaturityDateDetails" xlink:type="extended" id="i983f7006dd564371a85c346a3a80e367_InvestmentsInvestmentsClassifiedbyContractualMaturityDateDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_b7bf9cc2-9c9f-4936-b58e-033669b00156" 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_8eee49a4-903b-4f2c-9066-40fcf0484f7a" 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_b7bf9cc2-9c9f-4936-b58e-033669b00156" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_8eee49a4-903b-4f2c-9066-40fcf0484f7a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_6f259e65-86c0-4ef3-a4e2-34ad887b0403" 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_b7bf9cc2-9c9f-4936-b58e-033669b00156" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_6f259e65-86c0-4ef3-a4e2-34ad887b0403" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterFiveYearsFairValue_626e839b-7896-4043-a670-35931727f8cd" xlink:href="gntx-20220930.xsd#gntx_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_b7bf9cc2-9c9f-4936-b58e-033669b00156" xlink:to="loc_gntx_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterFiveYearsFairValue_626e839b-7896-4043-a670-35931727f8cd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_b8e9044a-3401-466d-bdf3-eb0a98163337" 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_b7bf9cc2-9c9f-4936-b58e-033669b00156" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_b8e9044a-3401-466d-bdf3-eb0a98163337" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_72701ad7-f875-46fd-a065-3d3faaf8ace6" 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_b7bf9cc2-9c9f-4936-b58e-033669b00156" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_72701ad7-f875-46fd-a065-3d3faaf8ace6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_e116ed68-ef01-4a41-8c5b-4ba26911c451" 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_72701ad7-f875-46fd-a065-3d3faaf8ace6" xlink:to="loc_us-gaap_FinancialInstrumentAxis_e116ed68-ef01-4a41-8c5b-4ba26911c451" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e116ed68-ef01-4a41-8c5b-4ba26911c451_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_e116ed68-ef01-4a41-8c5b-4ba26911c451" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_e116ed68-ef01-4a41-8c5b-4ba26911c451_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8ff71d3a-c641-47e0-8d6f-573cd15e4d81" 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_e116ed68-ef01-4a41-8c5b-4ba26911c451" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_8ff71d3a-c641-47e0-8d6f-573cd15e4d81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedIncomeSecuritiesMember_c29e64a2-5351-4f97-b8df-00af4cada556" 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_8ff71d3a-c641-47e0-8d6f-573cd15e4d81" xlink:to="loc_us-gaap_FixedIncomeSecuritiesMember_c29e64a2-5351-4f97-b8df-00af4cada556" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlansNarrativeDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#StockBasedCompensationPlansNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlansNarrativeDetails" xlink:type="extended" id="i346c56cd9bb64f68aac8131a7df21700_StockBasedCompensationPlansNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f8f94642-070a-4cd1-85ce-63a56db9217a" 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_e5d4548b-7915-481a-949f-557aa1a35821" xlink:href="gntx-20220930.xsd#gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfPlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f8f94642-070a-4cd1-85ce-63a56db9217a" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfPlans_e5d4548b-7915-481a-949f-557aa1a35821" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_6cc3d108-acd0-42c1-a144-b1dc1a41940d" 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_f8f94642-070a-4cd1-85ce-63a56db9217a" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_6cc3d108-acd0-42c1-a144-b1dc1a41940d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod_f008773d-2af6-4776-924b-0fa24ec0b5d2" xlink:href="gntx-20220930.xsd#gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f8f94642-070a-4cd1-85ce-63a56db9217a" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod_f008773d-2af6-4776-924b-0fa24ec0b5d2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_d5c99f54-5bff-44e5-b0ce-c5ca5cf3bf61" 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_f8f94642-070a-4cd1-85ce-63a56db9217a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_d5c99f54-5bff-44e5-b0ce-c5ca5cf3bf61" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_c06df97f-d18b-4dbe-b55d-f27ac30db456" 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_f8f94642-070a-4cd1-85ce-63a56db9217a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_c06df97f-d18b-4dbe-b55d-f27ac30db456" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_65004cd3-f870-4d00-a3ff-c541de468aee" 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_f8f94642-070a-4cd1-85ce-63a56db9217a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_65004cd3-f870-4d00-a3ff-c541de468aee" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_96d50454-8962-4bec-9fd7-973839f26a4a" 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_f8f94642-070a-4cd1-85ce-63a56db9217a" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_96d50454-8962-4bec-9fd7-973839f26a4a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_36dc0d44-57cb-40f5-8764-0ab5182a4662" 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_f8f94642-070a-4cd1-85ce-63a56db9217a" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_36dc0d44-57cb-40f5-8764-0ab5182a4662" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationRestrictedPeriod_611d9849-1481-4188-9552-f50ddbf0d9c3" xlink:href="gntx-20220930.xsd#gntx_ShareBasedCompensationRestrictedPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f8f94642-070a-4cd1-85ce-63a56db9217a" xlink:to="loc_gntx_ShareBasedCompensationRestrictedPeriod_611d9849-1481-4188-9552-f50ddbf0d9c3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockExpense_7849d4e2-ceac-42c8-baf3-4eca4a049cbd" 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_f8f94642-070a-4cd1-85ce-63a56db9217a" xlink:to="loc_us-gaap_RestrictedStockExpense_7849d4e2-ceac-42c8-baf3-4eca4a049cbd" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_e7413349-e9be-4986-b31f-14361932d00d" 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_f8f94642-070a-4cd1-85ce-63a56db9217a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_e7413349-e9be-4986-b31f-14361932d00d" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense_803dfb54-58c7-4ba9-99c4-f63fc66bf6fd" xlink:href="gntx-20220930.xsd#gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f8f94642-070a-4cd1-85ce-63a56db9217a" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense_803dfb54-58c7-4ba9-99c4-f63fc66bf6fd" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0ce9430a-6c86-46cf-891d-708574a1f893" 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_f8f94642-070a-4cd1-85ce-63a56db9217a" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0ce9430a-6c86-46cf-891d-708574a1f893" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_487e809e-bc18-439c-8e3d-d563f84f4aca" 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_0ce9430a-6c86-46cf-891d-708574a1f893" xlink:to="loc_us-gaap_AwardTypeAxis_487e809e-bc18-439c-8e3d-d563f84f4aca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_487e809e-bc18-439c-8e3d-d563f84f4aca_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_487e809e-bc18-439c-8e3d-d563f84f4aca" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_487e809e-bc18-439c-8e3d-d563f84f4aca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1411050b-5333-4e63-9db1-4b16db9453ad" 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_487e809e-bc18-439c-8e3d-d563f84f4aca" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1411050b-5333-4e63-9db1-4b16db9453ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockCompensationPlanMember_da05770e-2ab3-45ca-92c5-e9155aaf1d70" 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_1411050b-5333-4e63-9db1-4b16db9453ad" xlink:to="loc_us-gaap_StockCompensationPlanMember_da05770e-2ab3-45ca-92c5-e9155aaf1d70" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_344470f1-3f2c-4925-8c04-a5c13103aae7" 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_1411050b-5333-4e63-9db1-4b16db9453ad" xlink:to="loc_us-gaap_PerformanceSharesMember_344470f1-3f2c-4925-8c04-a5c13103aae7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_82eca638-3b97-4fbe-b99b-466d6af6c01c" 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_0ce9430a-6c86-46cf-891d-708574a1f893" xlink:to="loc_us-gaap_PlanNameAxis_82eca638-3b97-4fbe-b99b-466d6af6c01c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_82eca638-3b97-4fbe-b99b-466d6af6c01c_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_82eca638-3b97-4fbe-b99b-466d6af6c01c" xlink:to="loc_us-gaap_PlanNameDomain_82eca638-3b97-4fbe-b99b-466d6af6c01c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_723ec098-a742-4bba-b337-9d901b87571b" 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_82eca638-3b97-4fbe-b99b-466d6af6c01c" xlink:to="loc_us-gaap_PlanNameDomain_723ec098-a742-4bba-b337-9d901b87571b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OmnibusIncentivePlanMember_7f6c6bb9-f3c4-4dc6-bbcc-549a07c84004" xlink:href="gntx-20220930.xsd#gntx_OmnibusIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_723ec098-a742-4bba-b337-9d901b87571b" xlink:to="loc_gntx_OmnibusIncentivePlanMember_7f6c6bb9-f3c4-4dc6-bbcc-549a07c84004" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_EmployeeStockOptionPlanMember_b1c5fd2d-2ffd-4336-84b6-0c2d1442d9b4" xlink:href="gntx-20220930.xsd#gntx_EmployeeStockOptionPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_723ec098-a742-4bba-b337-9d901b87571b" xlink:to="loc_gntx_EmployeeStockOptionPlanMember_b1c5fd2d-2ffd-4336-84b6-0c2d1442d9b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_RestrictedStockPlanMember_7b8703ef-151c-4be3-a378-ae891516d685" xlink:href="gntx-20220930.xsd#gntx_RestrictedStockPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_723ec098-a742-4bba-b337-9d901b87571b" xlink:to="loc_gntx_RestrictedStockPlanMember_7b8703ef-151c-4be3-a378-ae891516d685" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_GentexCorporationEmployeeStockPurchasePlanMember_a8b29ba8-8e3e-459b-ba69-db40a16be4b2" xlink:href="gntx-20220930.xsd#gntx_GentexCorporationEmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_723ec098-a742-4bba-b337-9d901b87571b" xlink:to="loc_gntx_GentexCorporationEmployeeStockPurchasePlanMember_a8b29ba8-8e3e-459b-ba69-db40a16be4b2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_05e304ab-da77-4360-9b61-b7319768069a" 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_0ce9430a-6c86-46cf-891d-708574a1f893" xlink:to="loc_srt_RangeAxis_05e304ab-da77-4360-9b61-b7319768069a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_05e304ab-da77-4360-9b61-b7319768069a_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_05e304ab-da77-4360-9b61-b7319768069a" xlink:to="loc_srt_RangeMember_05e304ab-da77-4360-9b61-b7319768069a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_5cd1e050-1980-4c2e-8202-e72aba09bb5c" 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_05e304ab-da77-4360-9b61-b7319768069a" xlink:to="loc_srt_RangeMember_5cd1e050-1980-4c2e-8202-e72aba09bb5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_83a4ce4b-bf17-41d0-b270-3dac03c1247d" 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_5cd1e050-1980-4c2e-8202-e72aba09bb5c" xlink:to="loc_srt_MinimumMember_83a4ce4b-bf17-41d0-b270-3dac03c1247d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_ca678312-db03-498d-b4f0-4e5696f9e13a" 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_5cd1e050-1980-4c2e-8202-e72aba09bb5c" xlink:to="loc_srt_MaximumMember_ca678312-db03-498d-b4f0-4e5696f9e13a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_496a5ca0-b8a3-41f6-9165-bc3ec435a6ab" 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_0ce9430a-6c86-46cf-891d-708574a1f893" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_496a5ca0-b8a3-41f6-9165-bc3ec435a6ab" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_496a5ca0-b8a3-41f6-9165-bc3ec435a6ab_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_496a5ca0-b8a3-41f6-9165-bc3ec435a6ab" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_496a5ca0-b8a3-41f6-9165-bc3ec435a6ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_38ae745f-1291-4fa4-8162-985b8ea8abbd" 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_496a5ca0-b8a3-41f6-9165-bc3ec435a6ab" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_38ae745f-1291-4fa4-8162-985b8ea8abbd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_59d27792-d5ad-4f4d-8fc2-a4ae7cc85681" 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_38ae745f-1291-4fa4-8162-985b8ea8abbd" xlink:to="loc_us-gaap_EmployeeStockMember_59d27792-d5ad-4f4d-8fc2-a4ae7cc85681" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlansSharesIssuedNetofSharesCanceledExpiredDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#StockBasedCompensationPlansSharesIssuedNetofSharesCanceledExpiredDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlansSharesIssuedNetofSharesCanceledExpiredDetails" xlink:type="extended" id="i0cfb1ee24e804361992df2cfa2894fb1_StockBasedCompensationPlansSharesIssuedNetofSharesCanceledExpiredDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_16ebd380-f1c4-4fcc-8d57-95f50e0f7841" 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_3ec56eaf-354d-4701-813c-6afd75ff95bb" 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_16ebd380-f1c4-4fcc-8d57-95f50e0f7841" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_3ec56eaf-354d-4701-813c-6afd75ff95bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_84cd9895-a482-49f4-a9d7-d7beac9c0544" 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_16ebd380-f1c4-4fcc-8d57-95f50e0f7841" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_84cd9895-a482-49f4-a9d7-d7beac9c0544" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod_f05134df-a4b0-44fa-b377-6ea527622f9d" xlink:href="gntx-20220930.xsd#gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_16ebd380-f1c4-4fcc-8d57-95f50e0f7841" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedAwardGrantedInPeriod_f05134df-a4b0-44fa-b377-6ea527622f9d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsConversionRate_eaa692f4-f9af-4c10-a789-7eedbbc89da1" xlink:href="gntx-20220930.xsd#gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsConversionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_16ebd380-f1c4-4fcc-8d57-95f50e0f7841" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsConversionRate_eaa692f4-f9af-4c10-a789-7eedbbc89da1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentConversionRate_447691b0-1097-43a7-bffd-ee296dfd2cf4" xlink:href="gntx-20220930.xsd#gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentConversionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_16ebd380-f1c4-4fcc-8d57-95f50e0f7841" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentConversionRate_447691b0-1097-43a7-bffd-ee296dfd2cf4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_d80758fe-f654-451c-b83d-67dcea3274f8" 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_16ebd380-f1c4-4fcc-8d57-95f50e0f7841" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_d80758fe-f654-451c-b83d-67dcea3274f8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_80b7c26f-73eb-43da-9917-9db1995cb6c9" 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_16ebd380-f1c4-4fcc-8d57-95f50e0f7841" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_80b7c26f-73eb-43da-9917-9db1995cb6c9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_8d143a0c-abdf-4f88-b9ea-9dce07398a3a" 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_80b7c26f-73eb-43da-9917-9db1995cb6c9" xlink:to="loc_us-gaap_AwardTypeAxis_8d143a0c-abdf-4f88-b9ea-9dce07398a3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8d143a0c-abdf-4f88-b9ea-9dce07398a3a_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_8d143a0c-abdf-4f88-b9ea-9dce07398a3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8d143a0c-abdf-4f88-b9ea-9dce07398a3a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4c20cb50-82e2-48d5-b9cb-6e7c94dab205" 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_8d143a0c-abdf-4f88-b9ea-9dce07398a3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4c20cb50-82e2-48d5-b9cb-6e7c94dab205" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_NonQualifiedStockOptionMember_97f7913b-2ecd-400f-811f-819754fea76b" xlink:href="gntx-20220930.xsd#gntx_NonQualifiedStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_4c20cb50-82e2-48d5-b9cb-6e7c94dab205" xlink:to="loc_gntx_NonQualifiedStockOptionMember_97f7913b-2ecd-400f-811f-819754fea76b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_c93afba0-2e57-4c12-ac75-1e0e0b7c8256" 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_4c20cb50-82e2-48d5-b9cb-6e7c94dab205" xlink:to="loc_us-gaap_RestrictedStockMember_c93afba0-2e57-4c12-ac75-1e0e0b7c8256" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_4dc2cee2-3764-422a-9e90-c951c76155d4" 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_4c20cb50-82e2-48d5-b9cb-6e7c94dab205" xlink:to="loc_us-gaap_PerformanceSharesMember_4dc2cee2-3764-422a-9e90-c951c76155d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_96cf2479-431c-4d39-b59f-7c7aeb0de52d" 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_80b7c26f-73eb-43da-9917-9db1995cb6c9" xlink:to="loc_us-gaap_PlanNameAxis_96cf2479-431c-4d39-b59f-7c7aeb0de52d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_96cf2479-431c-4d39-b59f-7c7aeb0de52d_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_96cf2479-431c-4d39-b59f-7c7aeb0de52d" xlink:to="loc_us-gaap_PlanNameDomain_96cf2479-431c-4d39-b59f-7c7aeb0de52d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_95031ed5-6d21-4055-8391-76240a978d09" 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_96cf2479-431c-4d39-b59f-7c7aeb0de52d" xlink:to="loc_us-gaap_PlanNameDomain_95031ed5-6d21-4055-8391-76240a978d09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OmnibusIncentivePlanMember_956582c5-b6ca-4559-a88f-02901869e042" xlink:href="gntx-20220930.xsd#gntx_OmnibusIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_95031ed5-6d21-4055-8391-76240a978d09" xlink:to="loc_gntx_OmnibusIncentivePlanMember_956582c5-b6ca-4559-a88f-02901869e042" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncomeAOCIRollforwardDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#ComprehensiveIncomeAOCIRollforwardDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncomeAOCIRollforwardDetails" xlink:type="extended" id="ie828089de3374c1a8b2be5febe931c7c_ComprehensiveIncomeAOCIRollforwardDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_0036c6c7-43d1-4b7f-962f-1108ab70acba" 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_06d0aca7-6d26-483f-9299-a9d7ede8830f" 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_0036c6c7-43d1-4b7f-962f-1108ab70acba" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_06d0aca7-6d26-483f-9299-a9d7ede8830f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_43c5a545-565d-43b6-be6a-ba051a68409a" 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_06d0aca7-6d26-483f-9299-a9d7ede8830f" xlink:to="loc_us-gaap_StockholdersEquity_43c5a545-565d-43b6-be6a-ba051a68409a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_3ffb5d7d-844a-4a58-be48-a6b1e078c85d" 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_06d0aca7-6d26-483f-9299-a9d7ede8830f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_3ffb5d7d-844a-4a58-be48-a6b1e078c85d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_07240098-4333-41cc-8f61-67c7d2343e56" 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_06d0aca7-6d26-483f-9299-a9d7ede8830f" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_07240098-4333-41cc-8f61-67c7d2343e56" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_8bb9c1d9-b804-4ab1-ab25-ce2adac6c823" 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_06d0aca7-6d26-483f-9299-a9d7ede8830f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_8bb9c1d9-b804-4ab1-ab25-ce2adac6c823" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_5a041d11-7e20-4f50-90da-a25d9457ef08" 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_1527f75c-a8f4-40f3-a059-3b3012cbb7db" 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_0036c6c7-43d1-4b7f-962f-1108ab70acba" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_1527f75c-a8f4-40f3-a059-3b3012cbb7db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_34a265c4-0e01-410b-80a1-9c29a5969291" 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_0036c6c7-43d1-4b7f-962f-1108ab70acba" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_34a265c4-0e01-410b-80a1-9c29a5969291" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_e329524b-efee-4f96-8639-c61b91b9d478" 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_34a265c4-0e01-410b-80a1-9c29a5969291" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_e329524b-efee-4f96-8639-c61b91b9d478" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_e329524b-efee-4f96-8639-c61b91b9d478_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_e329524b-efee-4f96-8639-c61b91b9d478" xlink:to="loc_us-gaap_EquityComponentDomain_e329524b-efee-4f96-8639-c61b91b9d478_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_7b5f5fd6-d2b7-4727-a553-6abbe0387ac6" 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_e329524b-efee-4f96-8639-c61b91b9d478" xlink:to="loc_us-gaap_EquityComponentDomain_7b5f5fd6-d2b7-4727-a553-6abbe0387ac6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_7ad7b1d7-4b75-4da4-8ced-5f9553eb97ac" 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_7b5f5fd6-d2b7-4727-a553-6abbe0387ac6" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_7ad7b1d7-4b75-4da4-8ced-5f9553eb97ac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_bb20bf53-86ba-486c-870a-045f883e3eb1" 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_7ad7b1d7-4b75-4da4-8ced-5f9553eb97ac" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_bb20bf53-86ba-486c-870a-045f883e3eb1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_9c1e1438-4a1c-445d-a3e1-960167536a05" 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_7ad7b1d7-4b75-4da4-8ced-5f9553eb97ac" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_9c1e1438-4a1c-445d-a3e1-960167536a05" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncomeReclassificationOutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#ComprehensiveIncomeReclassificationOutofAccumulatedOtherComprehensiveIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncomeReclassificationOutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended" id="i4a554d5bdd6d4d17bd425d7a14c46c4c_ComprehensiveIncomeReclassificationOutofAccumulatedOtherComprehensiveIncomeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_343ca252-e86f-467f-9428-18290c0776bc" 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_864a6d67-9786-4377-8aac-4f9eb672bfd0" 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_343ca252-e86f-467f-9428-18290c0776bc" xlink:to="loc_us-gaap_EquitySecuritiesFvNiRealizedGainLoss_864a6d67-9786-4377-8aac-4f9eb672bfd0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_53abd430-c1e8-4b3c-bad2-8fe910da4eef" 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_343ca252-e86f-467f-9428-18290c0776bc" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_53abd430-c1e8-4b3c-bad2-8fe910da4eef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_9f21883d-0fd7-4d9a-bdb1-664f97978b8d" 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_343ca252-e86f-467f-9428-18290c0776bc" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_9f21883d-0fd7-4d9a-bdb1-664f97978b8d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_34407c32-1af7-4c98-b041-5dc290e5d6db" 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_343ca252-e86f-467f-9428-18290c0776bc" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_34407c32-1af7-4c98-b041-5dc290e5d6db" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_33f57d16-fb79-4849-9a44-86899a1e65cc" 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_34407c32-1af7-4c98-b041-5dc290e5d6db" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_33f57d16-fb79-4849-9a44-86899a1e65cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_33f57d16-fb79-4849-9a44-86899a1e65cc_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_33f57d16-fb79-4849-9a44-86899a1e65cc" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_33f57d16-fb79-4849-9a44-86899a1e65cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_59e31b02-6e0c-412a-a0ac-a49eb5da8aaf" 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_33f57d16-fb79-4849-9a44-86899a1e65cc" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_59e31b02-6e0c-412a-a0ac-a49eb5da8aaf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_f16e7114-c3f1-45a8-908d-ac921de0ea93" 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_59e31b02-6e0c-412a-a0ac-a49eb5da8aaf" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_f16e7114-c3f1-45a8-908d-ac921de0ea93" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_a5703d82-b56a-49e2-abc2-70dfd8e030bf" 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_34407c32-1af7-4c98-b041-5dc290e5d6db" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_a5703d82-b56a-49e2-abc2-70dfd8e030bf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_a5703d82-b56a-49e2-abc2-70dfd8e030bf_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_a5703d82-b56a-49e2-abc2-70dfd8e030bf" xlink:to="loc_us-gaap_EquityComponentDomain_a5703d82-b56a-49e2-abc2-70dfd8e030bf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_7a6fd7b9-d087-4cff-9f75-3ee20ecc205b" 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_a5703d82-b56a-49e2-abc2-70dfd8e030bf" xlink:to="loc_us-gaap_EquityComponentDomain_7a6fd7b9-d087-4cff-9f75-3ee20ecc205b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_29156560-49f4-461a-86b5-a22ded1a9233" 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_7a6fd7b9-d087-4cff-9f75-3ee20ecc205b" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_29156560-49f4-461a-86b5-a22ded1a9233" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/DebtandFinancingArrangementsDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#DebtandFinancingArrangementsDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/DebtandFinancingArrangementsDetails" xlink:type="extended" id="ia288ec5c6fd148c6af0fdc7ab43bf69e_DebtandFinancingArrangementsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_e218c7e1-0935-4110-87c8-2facbe408373" 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_d2e19eb3-8c34-48cb-9f5d-07bce06d0e34" 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_e218c7e1-0935-4110-87c8-2facbe408373" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_d2e19eb3-8c34-48cb-9f5d-07bce06d0e34" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount_efffce3a-bd28-484b-a54e-285a3a90249e" xlink:href="gntx-20220930.xsd#gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_e218c7e1-0935-4110-87c8-2facbe408373" xlink:to="loc_gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount_efffce3a-bd28-484b-a54e-285a3a90249e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_40c41472-506c-4963-926f-c95bb0274d95" 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_e218c7e1-0935-4110-87c8-2facbe408373" xlink:to="loc_us-gaap_LongTermDebt_40c41472-506c-4963-926f-c95bb0274d95" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_39b5d69b-1a84-4994-afc9-91f54eec5d7b" 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_e218c7e1-0935-4110-87c8-2facbe408373" xlink:to="loc_us-gaap_DebtInstrumentTable_39b5d69b-1a84-4994-afc9-91f54eec5d7b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_7401d142-7e98-4729-8c13-f92b5ee48c2e" 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_39b5d69b-1a84-4994-afc9-91f54eec5d7b" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_7401d142-7e98-4729-8c13-f92b5ee48c2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_7401d142-7e98-4729-8c13-f92b5ee48c2e_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_7401d142-7e98-4729-8c13-f92b5ee48c2e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_7401d142-7e98-4729-8c13-f92b5ee48c2e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_0058cc1b-a4cc-4951-b3f0-6ea13da9cef8" 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_7401d142-7e98-4729-8c13-f92b5ee48c2e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_0058cc1b-a4cc-4951-b3f0-6ea13da9cef8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_fb9a78c5-57ce-4b2e-9e82-8b15aab91230" 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_0058cc1b-a4cc-4951-b3f0-6ea13da9cef8" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_fb9a78c5-57ce-4b2e-9e82-8b15aab91230" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_040abcca-01ba-4a6d-96fc-ca9680a94b8a" 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_0058cc1b-a4cc-4951-b3f0-6ea13da9cef8" xlink:to="loc_us-gaap_LineOfCreditMember_040abcca-01ba-4a6d-96fc-ca9680a94b8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_SwingLoansMember_11dff981-0197-4ba9-b9f7-0828259ea5bc" xlink:href="gntx-20220930.xsd#gntx_SwingLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_0058cc1b-a4cc-4951-b3f0-6ea13da9cef8" xlink:to="loc_gntx_SwingLoansMember_11dff981-0197-4ba9-b9f7-0828259ea5bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_8a164b64-b9aa-4585-9bda-3cfdb4113e5a" 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_0058cc1b-a4cc-4951-b3f0-6ea13da9cef8" xlink:to="loc_us-gaap_LetterOfCreditMember_8a164b64-b9aa-4585-9bda-3cfdb4113e5a" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/SegmentReportingScheduleofAutomotiveandOtherSegmentReportingDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#SegmentReportingScheduleofAutomotiveandOtherSegmentReportingDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/SegmentReportingScheduleofAutomotiveandOtherSegmentReportingDetails" xlink:type="extended" id="ic10004ea02ff4c809a76ab7c99f763e8_SegmentReportingScheduleofAutomotiveandOtherSegmentReportingDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_18bb2a02-f17c-470b-b28d-79361943a265" 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_6d18072e-34fc-44b7-810d-8379eb474e32" 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_18bb2a02-f17c-470b-b28d-79361943a265" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_6d18072e-34fc-44b7-810d-8379eb474e32" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_3a057e84-16be-478d-825f-d8fe0a557043" 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_18bb2a02-f17c-470b-b28d-79361943a265" xlink:to="loc_us-gaap_OperatingIncomeLoss_3a057e84-16be-478d-825f-d8fe0a557043" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_3e3328fa-1498-4072-8146-1b0d29419810" 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_18bb2a02-f17c-470b-b28d-79361943a265" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_3e3328fa-1498-4072-8146-1b0d29419810" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_803b0696-fbb1-4c10-8ea4-243f0cf84ec6" 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_3e3328fa-1498-4072-8146-1b0d29419810" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_803b0696-fbb1-4c10-8ea4-243f0cf84ec6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_803b0696-fbb1-4c10-8ea4-243f0cf84ec6_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_803b0696-fbb1-4c10-8ea4-243f0cf84ec6" xlink:to="loc_us-gaap_SegmentDomain_803b0696-fbb1-4c10-8ea4-243f0cf84ec6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_b6b6f9c4-027c-4779-a09d-31e88ed697fe" 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_803b0696-fbb1-4c10-8ea4-243f0cf84ec6" xlink:to="loc_us-gaap_SegmentDomain_b6b6f9c4-027c-4779-a09d-31e88ed697fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveProductsSegmentMember_1ae9004c-8326-4957-ab25-30b4b62bf74a" xlink:href="gntx-20220930.xsd#gntx_AutomotiveProductsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_b6b6f9c4-027c-4779-a09d-31e88ed697fe" xlink:to="loc_gntx_AutomotiveProductsSegmentMember_1ae9004c-8326-4957-ab25-30b4b62bf74a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllOtherSegmentsMember_bf6f80a8-3bc9-49ca-8fe8-1deb20713316" 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_b6b6f9c4-027c-4779-a09d-31e88ed697fe" xlink:to="loc_us-gaap_AllOtherSegmentsMember_bf6f80a8-3bc9-49ca-8fe8-1deb20713316" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/RevenueDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#RevenueDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/RevenueDetails" xlink:type="extended" id="i256b2544110843f19ba66200d19d7934_RevenueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_e02a49fe-aba8-4a9c-aa50-3deb80de941f" 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_2ffcab5f-c777-42fa-a928-236d9e7f2c5f" 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_e02a49fe-aba8-4a9c-aa50-3deb80de941f" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_2ffcab5f-c777-42fa-a928-236d9e7f2c5f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_cfb6df71-3b8c-4462-a3b4-aa5e8a866926" 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_e02a49fe-aba8-4a9c-aa50-3deb80de941f" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_cfb6df71-3b8c-4462-a3b4-aa5e8a866926" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_0b2f3627-d3ea-497b-80ed-d1336e8179c6" 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_cfb6df71-3b8c-4462-a3b4-aa5e8a866926" xlink:to="loc_srt_StatementGeographicalAxis_0b2f3627-d3ea-497b-80ed-d1336e8179c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_0b2f3627-d3ea-497b-80ed-d1336e8179c6_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_0b2f3627-d3ea-497b-80ed-d1336e8179c6" xlink:to="loc_srt_SegmentGeographicalDomain_0b2f3627-d3ea-497b-80ed-d1336e8179c6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_cd333ab3-c94c-4721-8e78-f7358b71b46f" 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_0b2f3627-d3ea-497b-80ed-d1336e8179c6" xlink:to="loc_srt_SegmentGeographicalDomain_cd333ab3-c94c-4721-8e78-f7358b71b46f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_5c483bef-66d5-454c-8e20-acbe027e9fd8" 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_cd333ab3-c94c-4721-8e78-f7358b71b46f" xlink:to="loc_country_US_5c483bef-66d5-454c-8e20-acbe027e9fd8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_DE_891e22e3-d370-4d4b-85ad-65ab5c056a07" 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_cd333ab3-c94c-4721-8e78-f7358b71b46f" xlink:to="loc_country_DE_891e22e3-d370-4d4b-85ad-65ab5c056a07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_JP_8fd242d6-0fe6-4177-9770-ad92484d008f" 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_cd333ab3-c94c-4721-8e78-f7358b71b46f" xlink:to="loc_country_JP_8fd242d6-0fe6-4177-9770-ad92484d008f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_MX_9ea800af-7e8e-4f25-b17f-eb9599782f7a" 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_cd333ab3-c94c-4721-8e78-f7358b71b46f" xlink:to="loc_country_MX_9ea800af-7e8e-4f25-b17f-eb9599782f7a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OtherCountriesMember_93043d53-fd92-4b8f-bfa2-4cd585fa3734" xlink:href="gntx-20220930.xsd#gntx_OtherCountriesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cd333ab3-c94c-4721-8e78-f7358b71b46f" xlink:to="loc_gntx_OtherCountriesMember_93043d53-fd92-4b8f-bfa2-4cd585fa3734" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_e02d572d-855f-44d9-b4c0-89ae18869ebe" 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_cfb6df71-3b8c-4462-a3b4-aa5e8a866926" xlink:to="loc_srt_ProductOrServiceAxis_e02d572d-855f-44d9-b4c0-89ae18869ebe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_e02d572d-855f-44d9-b4c0-89ae18869ebe_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_e02d572d-855f-44d9-b4c0-89ae18869ebe" xlink:to="loc_srt_ProductsAndServicesDomain_e02d572d-855f-44d9-b4c0-89ae18869ebe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_66c2addb-6249-4614-9761-168eae6b4ba7" 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_e02d572d-855f-44d9-b4c0-89ae18869ebe" xlink:to="loc_srt_ProductsAndServicesDomain_66c2addb-6249-4614-9761-168eae6b4ba7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveProductsMember_eb29a6ae-2723-49f5-82fb-dd86bdad581c" xlink:href="gntx-20220930.xsd#gntx_AutomotiveProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_66c2addb-6249-4614-9761-168eae6b4ba7" xlink:to="loc_gntx_AutomotiveProductsMember_eb29a6ae-2723-49f5-82fb-dd86bdad581c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveMirrorsElectronicsMember_7d5521c5-7250-4429-b5f5-d689bc568beb" xlink:href="gntx-20220930.xsd#gntx_AutomotiveMirrorsElectronicsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_AutomotiveProductsMember_eb29a6ae-2723-49f5-82fb-dd86bdad581c" xlink:to="loc_gntx_AutomotiveMirrorsElectronicsMember_7d5521c5-7250-4429-b5f5-d689bc568beb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_HomeLinkModulesMember_fff11a90-173f-405d-ade9-fda086104d9e" xlink:href="gntx-20220930.xsd#gntx_HomeLinkModulesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_AutomotiveProductsMember_eb29a6ae-2723-49f5-82fb-dd86bdad581c" xlink:to="loc_gntx_HomeLinkModulesMember_fff11a90-173f-405d-ade9-fda086104d9e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OtherProductsMember_b0299d83-0e2d-438a-8c28-cc818a3c5119" xlink:href="gntx-20220930.xsd#gntx_OtherProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_66c2addb-6249-4614-9761-168eae6b4ba7" xlink:to="loc_gntx_OtherProductsMember_b0299d83-0e2d-438a-8c28-cc818a3c5119" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_FireProtectionProductsMember_cfe04b79-8737-4ac0-a041-876c5d0b8c96" xlink:href="gntx-20220930.xsd#gntx_FireProtectionProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_OtherProductsMember_b0299d83-0e2d-438a-8c28-cc818a3c5119" xlink:to="loc_gntx_FireProtectionProductsMember_cfe04b79-8737-4ac0-a041-876c5d0b8c96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AerospaceProductsMember_7c7e468b-e9a8-4ea5-81a1-914f62684dc6" xlink:href="gntx-20220930.xsd#gntx_AerospaceProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_OtherProductsMember_b0299d83-0e2d-438a-8c28-cc818a3c5119" xlink:to="loc_gntx_AerospaceProductsMember_7c7e468b-e9a8-4ea5-81a1-914f62684dc6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_fc99bed9-5f81-46e9-ae8a-f8dfc380e82b" 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_cfb6df71-3b8c-4462-a3b4-aa5e8a866926" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_fc99bed9-5f81-46e9-ae8a-f8dfc380e82b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_fc99bed9-5f81-46e9-ae8a-f8dfc380e82b_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_fc99bed9-5f81-46e9-ae8a-f8dfc380e82b" xlink:to="loc_us-gaap_SegmentDomain_fc99bed9-5f81-46e9-ae8a-f8dfc380e82b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_9c57f418-5db4-4dc4-8fea-c9def51342d9" 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_fc99bed9-5f81-46e9-ae8a-f8dfc380e82b" xlink:to="loc_us-gaap_SegmentDomain_9c57f418-5db4-4dc4-8fea-c9def51342d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveSegmentMember_f00b4ffb-cbf1-4c61-9df2-3b550da1512f" xlink:href="gntx-20220930.xsd#gntx_AutomotiveSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_9c57f418-5db4-4dc4-8fea-c9def51342d9" xlink:to="loc_gntx_AutomotiveSegmentMember_f00b4ffb-cbf1-4c61-9df2-3b550da1512f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OtherSegmentMember_33e6643b-14f6-4bfe-8da5-ebdd2f435e6a" xlink:href="gntx-20220930.xsd#gntx_OtherSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_9c57f418-5db4-4dc4-8fea-c9def51342d9" xlink:to="loc_gntx_OtherSegmentMember_33e6643b-14f6-4bfe-8da5-ebdd2f435e6a" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/LeasesDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#LeasesDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/LeasesDetails" xlink:type="extended" id="i856d6a51e4c94859a7e46630bd08af95_LeasesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_d4ba594c-3f1f-46db-b44f-31111d3e29ea" 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_62762da0-8fe3-4bc1-92fc-103ffa6d63ee" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_62762da0-8fe3-4bc1-92fc-103ffa6d63ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_42bf5008-32a3-4c4d-9925-3a3ba2e916db" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_42bf5008-32a3-4c4d-9925-3a3ba2e916db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_127adbe7-ffa3-4a32-bc61-42098677b1ce" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_127adbe7-ffa3-4a32-bc61-42098677b1ce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_28c31e63-543a-4819-903d-1f47f3c36e2c" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_28c31e63-543a-4819-903d-1f47f3c36e2c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_287a7dd2-668b-45d5-be7c-d2539625ea2b" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_287a7dd2-668b-45d5-be7c-d2539625ea2b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_7c95416b-712c-43ee-a05b-a9d923b47429" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_7c95416b-712c-43ee-a05b-a9d923b47429" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_95ffbd2e-9223-47e7-b8b1-198c7c5042d6" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_95ffbd2e-9223-47e7-b8b1-198c7c5042d6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_11059539-545e-4144-917b-011282ebd9ab" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_11059539-545e-4144-917b-011282ebd9ab" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour_807ac998-591a-4532-bceb-3966404923de" xlink:href="gntx-20220930.xsd#gntx_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_gntx_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour_807ac998-591a-4532-bceb-3966404923de" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_90fb73a5-cbef-47d5-b3e3-50e2e4505f52" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_90fb73a5-cbef-47d5-b3e3-50e2e4505f52" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_38c686fc-e363-4ff5-93f2-d5290a68c4fd" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_38c686fc-e363-4ff5-93f2-d5290a68c4fd" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_e864788b-fa6d-4003-a2f6-3ea34f775e26" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_OperatingLeaseLiability_e864788b-fa6d-4003-a2f6-3ea34f775e26" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_df2306ff-27b2-4639-9d70-55b5b7c65db4" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_df2306ff-27b2-4639-9d70-55b5b7c65db4" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_29052b3b-7400-4e96-b887-52399c76e4fb" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_29052b3b-7400-4e96-b887-52399c76e4fb" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_24a44c99-2205-43ec-b1b1-8cb2c5ca3451" 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_7a802491-a317-4d9f-814b-6070880dcf4b" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList_7a802491-a317-4d9f-814b-6070880dcf4b" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList_b1fdeae2-202f-4071-88e7-a931c6747d37" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList_b1fdeae2-202f-4071-88e7-a931c6747d37" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_bfe84b48-f243-426e-89a4-4a302e61eb1e" 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_d4ba594c-3f1f-46db-b44f-31111d3e29ea" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_bfe84b48-f243-426e-89a4-4a302e61eb1e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_ed6ca874-ea81-4b18-b292-9d93cd6357d1" 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_bfe84b48-f243-426e-89a4-4a302e61eb1e" xlink:to="loc_srt_RangeAxis_ed6ca874-ea81-4b18-b292-9d93cd6357d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_ed6ca874-ea81-4b18-b292-9d93cd6357d1_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_ed6ca874-ea81-4b18-b292-9d93cd6357d1" xlink:to="loc_srt_RangeMember_ed6ca874-ea81-4b18-b292-9d93cd6357d1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_dbd7c8d0-10d4-43f6-a114-8f6aa5693de6" 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_ed6ca874-ea81-4b18-b292-9d93cd6357d1" xlink:to="loc_srt_RangeMember_dbd7c8d0-10d4-43f6-a114-8f6aa5693de6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_c67fa15a-e8cc-40c2-b9e8-4a9ca75fc154" 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_dbd7c8d0-10d4-43f6-a114-8f6aa5693de6" xlink:to="loc_srt_MinimumMember_c67fa15a-e8cc-40c2-b9e8-4a9ca75fc154" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_8d065224-f930-4167-b16c-4f5f7119f445" 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_dbd7c8d0-10d4-43f6-a114-8f6aa5693de6" xlink:to="loc_srt_MaximumMember_8d065224-f930-4167-b16c-4f5f7119f445" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/AcquisitionDetails" xlink:type="simple" xlink:href="gntx-20220930.xsd#AcquisitionDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/AcquisitionDetails" xlink:type="extended" id="i7be24bc34ebd41e2a1750450e9807e75_AcquisitionDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_0bfe59c9-9d7f-4894-afbe-479c3dbadf89" 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_c68344d8-0523-44c1-aeaf-e7e7692aad7f" 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_0bfe59c9-9d7f-4894-afbe-479c3dbadf89" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_c68344d8-0523-44c1-aeaf-e7e7692aad7f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_015969c3-8e5e-4448-8610-6c0900b0a1d0" 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_0bfe59c9-9d7f-4894-afbe-479c3dbadf89" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_015969c3-8e5e-4448-8610-6c0900b0a1d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_faff5fb2-3a3c-4225-87cf-6c217cf1b14d" 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_0bfe59c9-9d7f-4894-afbe-479c3dbadf89" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_faff5fb2-3a3c-4225-87cf-6c217cf1b14d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_fb32e6ef-7b46-4ebe-ba43-1ad1e9f407e7" 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_faff5fb2-3a3c-4225-87cf-6c217cf1b14d" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_fb32e6ef-7b46-4ebe-ba43-1ad1e9f407e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_fb32e6ef-7b46-4ebe-ba43-1ad1e9f407e7_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_fb32e6ef-7b46-4ebe-ba43-1ad1e9f407e7" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_fb32e6ef-7b46-4ebe-ba43-1ad1e9f407e7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_37afb53b-0908-4ff6-9f51-4ba066ac36d0" 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_fb32e6ef-7b46-4ebe-ba43-1ad1e9f407e7" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_37afb53b-0908-4ff6-9f51-4ba066ac36d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_GuardianOpticalTechnologiesMember_4dda4e32-cb2a-4f92-b048-1a630f7a1fdf" xlink:href="gntx-20220930.xsd#gntx_GuardianOpticalTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_37afb53b-0908-4ff6-9f51-4ba066ac36d0" xlink:to="loc_gntx_GuardianOpticalTechnologiesMember_4dda4e32-cb2a-4f92-b048-1a630f7a1fdf" 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>
