<?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>0001873517</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>PAMELA CRAMER</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>7299</noOfUnitsSold>
            <aggregateMarketValue>336629.88</aggregateMarketValue>
            <noOfUnitsOutstanding>61133765</noOfUnitsOutstanding>
            <approxSaleDate>08/26/2024</approxSaleDate>
            <securitiesExchangeName>NASDAQ</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>08/26/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Exercise of Stock Options</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>7299</amountOfSecuritiesAcquired>
            <paymentDate>08/26/2024</paymentDate>
            <natureOfPayment>Cash</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>10b5-1 Sales for PAMELA CRAMER</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>08/09/2024</saleDate>
            <amountOfSecuritiesSold>49006</amountOfSecuritiesSold>
            <grossProceeds>2212496.73</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>08/26/2024</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>05/10/2024</planAdoptionDate>
            </planAdoptionDates>
            <signature>/s/ Pamela Cramer</signature>
        </noticeSignature>
    </formData>
</edgarSubmission>
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144
0001873517
XXXXXXXX
LIVE
0001649904
RHYTHM PHARMACEUTICALS INC
001-38223
222 Berkeley Street, 12th Floor
BOSTON
MA
02116
8572644280
PAMELA CRAMER
Officer
Common
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
8th Floor
New York
NY
10004
7299
336629.88
61133765
08/26/2024
NASDAQ
Common
08/26/2024
Exercise of Stock Options
Issuer
N
7299
08/26/2024
Cash
N
10b5-1 Sales for PAMELA CRAMER
222 Berkeley Street, 12th Floor
BOSTON
MA
02116
Common
08/09/2024
49006
2212496.73
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.
08/26/2024
05/10/2024
/s/ Pamela Cramer