<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
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      <filer>
        <filerCredentials>
          <cik>0001949593</cik>
          <ccc>XXXXXXXX</ccc>
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      <liveTestFlag>LIVE</liveTestFlag>



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    <issuerInfo>
      <issuerCik>0001701732</issuerCik>
      <issuerName>Altair Engineering Inc.</issuerName>
      <secFileNumber>001-38263</secFileNumber>
      <issuerAddress>
        <com:street1>1820 E. BIG BEAVER ROAD</com:street1>
        <com:city>TROY</com:city>
        <com:stateOrCountry>MI</com:stateOrCountry>
        <com:zipCode>48083</com:zipCode>
      </issuerAddress>
      <issuerContactPhone>248-614-2400</issuerContactPhone>
      <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>Kunju Ravi</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
      <relationshipsToIssuer>
        <relationshipToIssuer>Officer</relationshipToIssuer>
      </relationshipsToIssuer>
    </issuerInfo>
    <securitiesInformation>
      <securitiesClassTitle>Class A Common Stock</securitiesClassTitle>
      <brokerOrMarketmakerDetails>
        <name>Morgan Stanley Smith Barney LLC</name>
        <address>
          <com:street1>Harborside 2</com:street1>
          <com:street2>200 Hudson Street, Suite 501</com:street2>
          <com:city>Jersey City</com:city>
          <com:stateOrCountry>NJ</com:stateOrCountry>
          <com:zipCode>07311</com:zipCode>
        </address>
      </brokerOrMarketmakerDetails>
      <noOfUnitsSold>228</noOfUnitsSold>
      <aggregateMarketValue>25387.80</aggregateMarketValue>
      <noOfUnitsOutstanding>60401224</noOfUnitsOutstanding>
      <approxSaleDate>03/18/2025</approxSaleDate>
      <securitiesExchangeName>NASDAQ</securitiesExchangeName>
    </securitiesInformation>
    <securitiesToBeSold>
      <securitiesClassTitle>Class A Common Stock</securitiesClassTitle>
      <acquiredDate>03/15/2025</acquiredDate>
      <natureOfAcquisitionTransaction>Class A Common Stock Restricted Stock Unit Vesting</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>751</amountOfSecuritiesAcquired>
      <paymentDate>03/15/2025</paymentDate>
      <natureOfPayment>N/A</natureOfPayment>
    </securitiesToBeSold>
    <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Ravi Kunju</name>
        <address>
          <com:street1>1820 E. Big Beaver Rd.</com:street1>
          <com:city>Troy</com:city>
          <com:stateOrCountry>MI</com:stateOrCountry>
          <com:zipCode>48083</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Class A Common Stock</securitiesClassTitle>
      <saleDate>02/26/2025</saleDate>
      <amountOfSecuritiesSold>120</amountOfSecuritiesSold>
      <grossProceeds>13383.60</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Ravi Kunju</name>
        <address>
          <com:street1>1820 E. Big Beaver Rd.</com:street1>
          <com:city>Troy</com:city>
          <com:stateOrCountry>MI</com:stateOrCountry>
          <com:zipCode>48083</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Class A Common Stock</securitiesClassTitle>
      <saleDate>03/03/2025</saleDate>
      <amountOfSecuritiesSold>121</amountOfSecuritiesSold>
      <grossProceeds>13485.45</grossProceeds>
    </securitiesSoldInPast3Months>
    <remarks>Represents registered Class A common stock to be sold pursuant to the Issuer's 2017 Equity Incentive Plan for sell-to-cover transactions for tax withholding obligations resulting from the vesting of Class A common stock restricted stock units.</remarks>
    <noticeSignature>
      <noticeDate>03/18/2025</noticeDate>
      <signature>Ravi Kunju</signature>
    </noticeSignature>
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144
0001949593
XXXXXXXX
LIVE
0001701732
Altair Engineering Inc.
001-38263
1820 E. BIG BEAVER ROAD
TROY
MI
48083
248-614-2400
Kunju Ravi
Officer
Class A Common Stock
Morgan Stanley Smith Barney LLC
Harborside 2
200 Hudson Street, Suite 501
Jersey City
NJ
07311
228
25387.80
60401224
03/18/2025
NASDAQ
Class A Common Stock
03/15/2025
Class A Common Stock Restricted Stock Unit Vesting
Issuer
N
751
03/15/2025
N/A
N
Ravi Kunju
1820 E. Big Beaver Rd.
Troy
MI
48083
Class A Common Stock
02/26/2025
120
13383.60
Ravi Kunju
1820 E. Big Beaver Rd.
Troy
MI
48083
Class A Common Stock
03/03/2025
121
13485.45
Represents registered Class A common stock to be sold pursuant to the Issuer's 2017 Equity Incentive Plan for sell-to-cover transactions for tax withholding obligations resulting from the vesting of Class A common stock restricted stock units.
03/18/2025
Ravi Kunju