Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2022	Aug. 08, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Trading Symbol	AMLX
Entity Registrant Name	Amylyx Pharmaceuticals, Inc.
Entity Central Index Key	0001658551
Current Fiscal Year End Date	--12-31
Entity File Number	001-41199
Entity Tax Identification Number	46-4600503
Entity Address, Address Line One	43 Thorndike St.
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02141
City Area Code	617
Local Phone Number	682-0917
Entity Current Reporting Status	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 Common Stock, Shares Outstanding		58,533,226
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false