Thibodeau Bay is a freshwater body located in the north central part of the Gouin Reservoir, in the territory of the town of La Tuque, in the administrative region of the Mauricie, in the province of Quebec, in Canada.

The surface of Thibodeau Bay is usually frozen from mid-November to the end of April, however, safe ice circulation is generally from early December to late March.

The rest of the west side of Thibodeau Bay is bounded by a series of islands that stand out on the Du Mâle Lake (Gouin Reservoir).

On the east side, this bay flows eastward by two straits in the Bourgeois Lake (Gouin Reservoir) bypassing the latter island.

The French toponym "Baie Thibodeau" was formalized on December 18, 1986, by the Commission de toponymie du Québec.