Opémisca Lake is a freshwater body of the Eeyou Istchee Baie-James, in Jamésie, in the administrative region of Nord-du-Québec, in the province of Quebec, in Canada.

Recreotourism activities, especially boating and vacationing, are popular, particularly because of the proximity of the village of Chapais, located in the south.

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

Lake Opemisca is fed on the east side by the Chibougamau River which crosses the "Rapides Entre les Îles" where a bridge is laid out for the forest road leading north.

Most islands are in the northwestern part of the lake; the largest being "La Grosse Île" (length: 4.2 kilometres (2.6 mi)) that straddles the townships of Opémisca and Cuvier.

According to information obtained from the local band council, this would be a Cree word meaning "difficult to extirpate".

[2] The toponym "Lake Opémisca" was made official on December 5, 1968 by the Commission de toponymie du Québec during its creation.