Lac Sakami is a lake in the northwest of the province of Quebec in Canada.

It is located east of James Bay, south of the Robert-Bourassa Reservoir and north of the Opinaca Reservoir.

Lac Sakami is now a reservoir of the James Bay Project with a depth of 113 m (371 ft), an elevation of 186 m (610 ft) and an area of 738 km2 (285 sq mi).

Prior to being used as a reservoir it had an area of 533 km2 (206 sq mi).

The Cree called the lake Mesackamee.