| Document and Entity Information | Dec. 18, 2024 |
| Document and Entity Information [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Dec. 18, 2024 |
| Entity File Number | 001-37809 |
| Entity Registrant Name | METAVIA INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 47-2389984 |
| Entity Address, Address Line One | 545 Concord Avenue |
| Entity Address, Adress Line Two | Suite 210 |
| Entity Address, City or Town | Cambridge |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02138 |
| City Area Code | 857 |
| Local Phone Number | 702-9600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.001 per share |
| Trading Symbol | MTVA |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001638287 |
| Amendment Flag | false |
