| Antoine Castonguay | |
| Office: | Member of the Legislative Assembly of Quebec for Roberval |
| Predecessor: | Émile Moreau |
| Successor: | Georges Potvin |
| Term Start: | 1935 |
| Term End: | 1939 |
| Birth Date: | 14 June 1881 |
| Birth Place: | Sainte-Hélène, near Kamouraska, Quebec |
| Death Place: | Chicoutimi, Quebec |
| Party: | Action libérale nationale Union Nationale |
Antoine Castonguay (June 14, 1881 - May 11, 1959) was a politician in Quebec, Canada and a Member of the Legislative Assembly of Quebec (MLA).
He was born on June 14, 1881, near Kamouraska, Bas-Saint-Laurent.
Castonguay served as Mayor of Saint-Félicien in Saguenay-Lac-Saint-Jean from 1935 to 1940.
He ran as an Action libérale nationale candidate in the district of Roberval in the 1935 provincial election and won. Castonguay joined Maurice Duplessis's Union Nationale and was re-elected in 1936. He was defeated by Liberal candidate Georges Potvin in 1939.
He died on May 11, 1959, in Chicoutimi.