Annual report pursuant to Section 13 and 15(d)


Cover - USD ($)
$ in Millions
12 Months Ended
Mar. 31, 2021
Jun. 01, 2021
Sep. 30, 2020
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Mar. 31, 2021    
Document Transition Report false    
Entity File Number 001-38906    
Entity Registrant Name IMMUNOVANT, INC.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 83-2771572    
Entity Address, Address Line One 320 West 37th Street    
Entity Address, City or Town New York,    
Entity Address, State or Province NY    
Entity Address, Postal Zip Code 10018    
City Area Code 917    
Local Phone Number 580-3099    
Title of 12(b) Security Common Stock, $0.0001 par value per share    
Trading Symbol IMVT    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Entity Shell Company false    
Entity Public Float     $ 1,460.5
Entity Common Stock, Shares Outstanding   97,976,695  
Entity Central Index Key 0001764013    
Amendment Flag false    
Current Fiscal Year End Date --03-31    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2020