Cover - shares	9 Months Ended
	Sep. 30, 2024	Nov. 04, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2024
Document Transition Report	false
Entity File Number	001-40693
Entity Registrant Name	RALLYBIO CORPORATION
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	85-1083789
Entity Address, Address Line One	234 Church Street
Entity Address, Address Line Two	Suite 1020
Entity Address, City or Town	New Haven
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06510
City Area Code	203
Local Phone Number	859-3820
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	RLYB
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Bankruptcy Proceedings, Reporting Current	true
Entity Common Stock, Shares Outstanding (in shares)		41,487,586
Entity Central Index Key	0001739410
Document Fiscal Year Focus	2024
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q3
Amendment Flag	false