<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
  <headerData>
    <submissionType>144</submissionType>
    <filerInfo>
      <filer>
        <filerCredentials>
          <cik>0001249802</cik>
          <ccc>XXXXXXXX</ccc>
        </filerCredentials>
      </filer>
      <liveTestFlag>LIVE</liveTestFlag>



    </filerInfo>
  </headerData>
  <formData>
    <issuerInfo>
      <issuerCik>0000883241</issuerCik>
      <issuerName>SYNOPSYS INC</issuerName>
      <secFileNumber>000-19807</secFileNumber>
      <issuerAddress>
        <com:street1>675 ALMANOR AVE</com:street1>
        <com:city>SUNNYVALE</com:city>
        <com:stateOrCountry>CA</com:stateOrCountry>
        <com:zipCode>94085</com:zipCode>
      </issuerAddress>
      <issuerContactPhone>6505845000</issuerContactPhone>
      <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>DE GEUS AART</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
      <relationshipsToIssuer>
        <relationshipToIssuer>Officer</relationshipToIssuer>
        <relationshipToIssuer>Director</relationshipToIssuer>
      </relationshipsToIssuer>
    </issuerInfo>
    <securitiesInformation>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <brokerOrMarketmakerDetails>
        <name>UBS Financial Services Inc.</name>
        <address>
          <com:street1>1000 Harbor Boulevard</com:street1>
          <com:street2>3rd Floor</com:street2>
          <com:city>Weehawken</com:city>
          <com:stateOrCountry>NJ</com:stateOrCountry>
          <com:zipCode>07086</com:zipCode>
        </address>
      </brokerOrMarketmakerDetails>
      <noOfUnitsSold>34882</noOfUnitsSold>
      <aggregateMarketValue>21684395.30</aggregateMarketValue>
      <noOfUnitsOutstanding>153216093</noOfUnitsOutstanding>
      <approxSaleDate>07/08/2024</approxSaleDate>
      <securitiesExchangeName>NASDAQ</securitiesExchangeName>
    </securitiesInformation>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>07/08/2024</acquiredDate>
      <natureOfAcquisitionTransaction>Exercise of Stock Option</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>34882</amountOfSecuritiesAcquired>
      <paymentDate>07/08/2024</paymentDate>
      <natureOfPayment>Cash</natureOfPayment>
    </securitiesToBeSold>
    <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Aart De Geus</name>
        <address>
          <com:street1>675 ALMANOR AVE</com:street1>
          <com:city>Sunnyvale</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>94085</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>06/24/2024</saleDate>
      <amountOfSecuritiesSold>2535</amountOfSecuritiesSold>
      <grossProceeds>1523497.99</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Aart De Geus</name>
        <address>
          <com:street1>675 ALMANOR AVE,</com:street1>
          <com:city>Sunnyvale</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>94085</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>06/25/2024</saleDate>
      <amountOfSecuritiesSold>4212</amountOfSecuritiesSold>
      <grossProceeds>2527413.97</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Aart De Geus</name>
        <address>
          <com:street1>675 ALMANOR AVE,</com:street1>
          <com:city>Sunnyvale</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>94085</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>06/26/2024</saleDate>
      <amountOfSecuritiesSold>2899</amountOfSecuritiesSold>
      <grossProceeds>1741062.00</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Aart De Geus</name>
        <address>
          <com:street1>675 ALMANOR AVE,</com:street1>
          <com:city>Sunnyvale</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>94085</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>06/27/2024</saleDate>
      <amountOfSecuritiesSold>8158</amountOfSecuritiesSold>
      <grossProceeds>4915912.90</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Aart De Geus</name>
        <address>
          <com:street1>675 ALMANOR AVE,</com:street1>
          <com:city>Sunnyvale</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>94085</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>06/28/2024</saleDate>
      <amountOfSecuritiesSold>11185</amountOfSecuritiesSold>
      <grossProceeds>6755056.60</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Aart De Geus</name>
        <address>
          <com:street1>675 ALMANOR AVE,</com:street1>
          <com:city>Sunnyvale</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>94085</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>07/01/2024</saleDate>
      <amountOfSecuritiesSold>5893</amountOfSecuritiesSold>
      <grossProceeds>3547563.61</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Aart De Geus</name>
        <address>
          <com:street1>675 ALMANOR AVE,</com:street1>
          <com:city>Sunnyvale</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>94085</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>07/02/2024</saleDate>
      <amountOfSecuritiesSold>4340</amountOfSecuritiesSold>
      <grossProceeds>2648497.56</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Aart de Geus</name>
        <address>
          <com:street1>675 ALMANOR AVE.</com:street1>
          <com:city>Sunnyvale</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>94085</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>07/03/2024</saleDate>
      <amountOfSecuritiesSold>2789</amountOfSecuritiesSold>
      <grossProceeds>1703912.22</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Aart de Geus</name>
        <address>
          <com:street1>675 ALMANOR AVE.</com:street1>
          <com:city>Sunnyvale</com:city>
          <com:stateOrCountry>CA</com:stateOrCountry>
          <com:zipCode>94085</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>07/05/2024</saleDate>
      <amountOfSecuritiesSold>27753</amountOfSecuritiesSold>
      <grossProceeds>17167470.17</grossProceeds>
    </securitiesSoldInPast3Months>
    <noticeSignature>
      <noticeDate>07/08/2024</noticeDate>
      <planAdoptionDates>
        <planAdoptionDate>03/25/2024</planAdoptionDate>
      </planAdoptionDates>
      <signature>/s/ UBS Financial Services Inc. as attorney-in-fact for Aart De Geus</signature>
    </noticeSignature>
  </formData>
</edgarSubmission>
