content: <?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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    <headerData>
      <submissionType>144</submissionType>
      <filerInfo>
        <filer>
          <filerCredentials>
            <cik>0001720314</cik>
            <ccc>XXXXXXXX</ccc>
          </filerCredentials>
        </filer>
        <liveTestFlag>LIVE</liveTestFlag>
  
  
  
      </filerInfo>
    </headerData>
    <formData>
      <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>James Ralph Scapa</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>CEO</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>Class A Common</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>J.P. Morgan Securities LLC</name>
          <address>
            <com:street1>390 Madison Avenue</com:street1>
            <com:street2>6th Floor</com:street2>
            <com:city>New York</com:city>
            <com:stateOrCountry>NY</com:stateOrCountry>
            <com:zipCode>10017</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>30000</noOfUnitsSold>
        <aggregateMarketValue>2494200</aggregateMarketValue>
        <noOfUnitsOutstanding>54627196</noOfUnitsOutstanding>
        <approxSaleDate>01/16/2024</approxSaleDate>
        <securitiesExchangeName>NASDAQ</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>Class A Common</securitiesClassTitle>
        <acquiredDate>11/01/2017</acquiredDate>
        <natureOfAcquisitionTransaction>Direct Investment by the James R. Scapa Declaration of Trust dated 03/05/87</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>15000</amountOfSecuritiesAcquired>
        <paymentDate>11/01/2017</paymentDate>
        <natureOfPayment>N/A</natureOfPayment>
      </securitiesToBeSold>
      <securitiesToBeSold>
        <securitiesClassTitle>Class A Common</securitiesClassTitle>
        <acquiredDate>11/01/2017</acquiredDate>
        <natureOfAcquisitionTransaction>Direct Investment by the JRS Investments LLC</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>15000</amountOfSecuritiesAcquired>
        <paymentDate>11/01/2017</paymentDate>
        <natureOfPayment>N/A</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>James Scapa Declaration of Trust</name>
          <address>
            <com:street1>C/o Altair Engineering, Inc.</com:street1>
            <com:street2>1820 E. Big Beaver Road</com:street2>
            <com:city>Troy</com:city>
            <com:stateOrCountry>MI</com:stateOrCountry>
            <com:zipCode>48083</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Class A Common</securitiesClassTitle>
        <saleDate>11/16/2023</saleDate>
        <amountOfSecuritiesSold>5000</amountOfSecuritiesSold>
        <grossProceeds>362609</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>James Scapa Declaration of Trust</name>
          <address>
            <com:street1>C/o Altair Engineering, Inc.</com:street1>
            <com:street2>1820 E. Big Beaver Road</com:street2>
            <com:city>Troy</com:city>
            <com:stateOrCountry>MI</com:stateOrCountry>
            <com:zipCode>48083</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Class A Common</securitiesClassTitle>
        <saleDate>12/18/2023</saleDate>
        <amountOfSecuritiesSold>5000</amountOfSecuritiesSold>
        <grossProceeds>370575</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>JRS Investments LLC</name>
          <address>
            <com:street1>C/o Altair Engineering, Inc.</com:street1>
            <com:street2>1820 E. Big Beaver Road</com:street2>
            <com:city>Troy</com:city>
            <com:stateOrCountry>MI</com:stateOrCountry>
            <com:zipCode>48083</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Class A Common</securitiesClassTitle>
        <saleDate>11/16/2023</saleDate>
        <amountOfSecuritiesSold>5000</amountOfSecuritiesSold>
        <grossProceeds>362609</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>JRS Investments LLC</name>
          <address>
            <com:street1>C/o Altair Engineering, Inc.</com:street1>
            <com:street2>1820 E. Big Beaver Road</com:street2>
            <com:city>Troy</com:city>
            <com:stateOrCountry>MI</com:stateOrCountry>
            <com:zipCode>48083</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Class A Common</securitiesClassTitle>
        <saleDate>12/18/2023</saleDate>
        <amountOfSecuritiesSold>5000</amountOfSecuritiesSold>
        <grossProceeds>370575</grossProceeds>
      </securitiesSoldInPast3Months>
      <remarks>Of the 30,000 shares being filed,  15,000 shares will be sold by the James R. Scapa Declaration of Trust dated 03/05/87, James R. Scapa as Trustee and 15,000 shares will be sold by the JRS Investments LLC, James R. Scapa as Manager</remarks>
      <noticeSignature>
        <noticeDate>01/16/2024</noticeDate>
        <planAdoptionDates>
          <planAdoptionDate>12/14/2022</planAdoptionDate>
        </planAdoptionDates>
        <signature>/s/ J.P. Morgan Securities LLC as agent and attorney-in-fact for James Ralph Scapa</signature>
      </noticeSignature>
    </formData>
  </edgarSubmission>
metadata_documents: [{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 6508}]
text: 144
  0001720314
  XXXXXXXX
  LIVE
  0001701732
  Altair Engineering, Inc.
  001-38263
  1820 E. Big Beaver Road
  Troy
  MI
  48083
  248-614-2400
  James Ralph Scapa
  CEO
  Class A Common
  J.P. Morgan Securities LLC
  390 Madison Avenue
  6th Floor
  New York
  NY
  10017
  30000
  2494200
  54627196
  01/16/2024
  NASDAQ
  Class A Common
  11/01/2017
  Direct Investment by the James R. Scapa Declaration of Trust dated 03/05/87
  Issuer
  N
  15000
  11/01/2017
  N/A
  Class A Common
  11/01/2017
  Direct Investment by the JRS Investments LLC
  Issuer
  N
  15000
  11/01/2017
  N/A
  N
  James Scapa Declaration of Trust
  C/o Altair Engineering, Inc.
  1820 E. Big Beaver Road
  Troy
  MI
  48083
  Class A Common
  11/16/2023
  5000
  362609
  James Scapa Declaration of Trust
  C/o Altair Engineering, Inc.
  1820 E. Big Beaver Road
  Troy
  MI
  48083
  Class A Common
  12/18/2023
  5000
  370575
  JRS Investments LLC
  C/o Altair Engineering, Inc.
  1820 E. Big Beaver Road
  Troy
  MI
  48083
  Class A Common
  11/16/2023
  5000
  362609
  JRS Investments LLC
  C/o Altair Engineering, Inc.
  1820 E. Big Beaver Road
  Troy
  MI
  48083
  Class A Common
  12/18/2023
  5000
  370575
  Of the 30,000 shares being filed,  15,000 shares will be sold by the James R. Scapa Declaration of Trust dated 03/05/87, James R. Scapa as Trustee and 15,000 shares will be sold by the JRS Investments LLC, James R. Scapa as Manager
  01/16/2024
  12/14/2022
  /s/ J.P. Morgan Securities LLC as agent and attorney-in-fact for James Ralph Scapa