The Théodat River is a tributary of Evans Lake, in Regional County Municipality (MRC) of Eeyou Istchee Baie-James (municipality), in the administrative region from Nord-du-Québec, Canadian province of Quebec, in Canada.

The surface of the river is usually frozen from early November to mid-May, however, safe ice circulation is generally from mid-November to mid-April.

The main hydrographic slopes near the Théodat River are: The Theodat River originates at the mouth of a little unidentified lake (length: 0.6 kilometres (0.37 mi) altitude: 317 metres (1,040 ft)).

This source is located at: From its source, the Théodat River flows on 117.4 kilometres (72.9 mi) according to the following segments: Upper part of Theodat River (segment of 50.1 kilometres (31.1 mi) crossing the Assinica Wildlife Sanctuary) Lower part of Théodat River (segment of 67.3 kilometres (41.8 mi)) The Theodat River flows into the Northeast bay of Evans Lake, facing an island with a length of 1.1 kilometres (0.68 mi).

The mouth of Théodat River is located at: The toponym "Théodat River" was formalized on December 5, 1968, at the Commission de toponymie du Québec, i.e. at the creation of this commission[3] Download coordinates as: