Document and Entity Information - shares
3 Months Ended
Jun. 30, 2018
Aug. 29, 2018
Document And Entity Information    
Entity Registrant Name Replimune Group, Inc.  
Entity Central Index Key 0001737953  
Document Type 10-Q  
Document Period End Date Jun. 30, 2018  
Amendment Flag false  
Current Fiscal Year End Date --03-31  
Entity Current Reporting Status No  
Entity Filer Category Non-accelerated Filer  
Entity Common Stock, Shares Outstanding   31,553,672
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q1