| Document and Entity Information | Sep. 30, 2022 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001658551 |
| Document Type | 8-K |
| Document Period End Date | Sep. 30, 2022 |
| Entity Registrant Name | AMYLYX PHARMACEUTICALS, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-41199 |
| Entity Tax Identification Number | 46-4600503 |
| Entity Address, Address Line One | 43 Thorndike |
| Entity Address, Address Line Two | 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $0.0001 par value per share |
| Trading Symbol | AMLX |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
