<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:ns2="http://www.sec.gov/edgar/common">
    <headerData>
        <submissionType>144</submissionType>
        <filerInfo>
            <filer>
                <filerCredentials>
                    <cik>0001909855</cik>
                    <ccc>XXXXXXXX</ccc>
                </filerCredentials>
            </filer>
            <liveTestFlag>LIVE</liveTestFlag>



        </filerInfo>
    </headerData>
    <formData>
        <issuerInfo>
            <issuerCik>0001649904</issuerCik>
            <issuerName>RHYTHM PHARMACEUTICALS INC</issuerName>
            <secFileNumber>001-38223</secFileNumber>
            <issuerAddress>
                <ns2:street1>222 Berkeley Street, 12th Floor</ns2:street1>
                <ns2:city>BOSTON</ns2:city>
                <ns2:stateOrCountry>MA</ns2:stateOrCountry>
                <ns2:zipCode>02116</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>8572644280</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>JOSEPH  SHULMAN</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Officer</relationshipToIssuer>
            </relationshipsToIssuer>
        </issuerInfo>
        <securitiesInformation>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <brokerOrMarketmakerDetails>
                <name>Morgan Stanley Smith Barney LLC Executive Financial Services</name>
                <address>
                    <ns2:street1>1 New York Plaza</ns2:street1>
                    <ns2:street2>8th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10004</ns2:zipCode>
                </address>
            </brokerOrMarketmakerDetails>
            <noOfUnitsSold>10625</noOfUnitsSold>
            <aggregateMarketValue>495125.00</aggregateMarketValue>
            <noOfUnitsOutstanding>60972909</noOfUnitsOutstanding>
            <approxSaleDate>07/12/2024</approxSaleDate>
            <securitiesExchangeName>NASDAQ</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>07/12/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Exercise of Stock Options</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>10625</amountOfSecuritiesAcquired>
            <paymentDate>07/12/2024</paymentDate>
            <natureOfPayment>Cash</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>10b5-1 Sales for JOSEPH J SHULMAN</name>
                <address>
                    <ns2:street1>222 Berkeley Street, 12th Floor</ns2:street1>
                    <ns2:city>BOSTON</ns2:city>
                    <ns2:stateOrCountry>MA</ns2:stateOrCountry>
                    <ns2:zipCode>02116</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>05/09/2024</saleDate>
            <amountOfSecuritiesSold>3984</amountOfSecuritiesSold>
            <grossProceeds>153258.50</grossProceeds>
        </securitiesSoldInPast3Months>
        <remarks>The securities to be sold were and will be received upon the exercise of stock options over the next three months. The dates of acquisition and payment were and will be the dates of exercise/sale.&#13;
</remarks>
        <noticeSignature>
            <noticeDate>07/12/2024</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>05/05/2023</planAdoptionDate>
            </planAdoptionDates>
            <signature>/s/ Joseph Shulman</signature>
        </noticeSignature>
    </formData>
</edgarSubmission>
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144
0001909855
XXXXXXXX
LIVE
0001649904
RHYTHM PHARMACEUTICALS INC
001-38223
222 Berkeley Street, 12th Floor
BOSTON
MA
02116
8572644280
JOSEPH  SHULMAN
Officer
Common
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
8th Floor
New York
NY
10004
10625
495125.00
60972909
07/12/2024
NASDAQ
Common
07/12/2024
Exercise of Stock Options
Issuer
N
10625
07/12/2024
Cash
N
10b5-1 Sales for JOSEPH J SHULMAN
222 Berkeley Street, 12th Floor
BOSTON
MA
02116
Common
05/09/2024
3984
153258.50
The securities to be sold were and will be received upon the exercise of stock options over the next three months. The dates of acquisition and payment were and will be the dates of exercise/sale.
07/12/2024
05/05/2023
/s/ Joseph Shulman