v3.26.1
Cover - shares
 3 Months Ended
Mar. 31, 2026
May 01, 2026
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2026  
Document Transition Report false  
Entity File Number 001-38223  
Entity Registrant Name RHYTHM PHARMACEUTICALS, INC.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 46-2159271  
Entity Address, Address Line One 222 Berkeley Street  
Entity Address, Address Line Two 12th Floor  
Entity Address, City or Town Boston  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 02116  
City Area Code 857  
Local Phone Number 264-4280  
Title of 12(b) Security Common Stock, $0.001 par value per share  
Trading Symbol RYTM  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   68,532,607
Entity Central Index Key 0001649904  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q1  
Amendment Flag false