Lac Grandbois is a freshwater body straddling the municipalities of Rivière-à-Pierre (southern part of the lake) and Saint-Raymond (northern part of the lake), in Portneuf Regional County Municipality, in the administrative region of Capitale-Nationale, in the province of Quebec, in Canada.

The west side of the lake is served by a forest road linking north the main street of Rivière-à-Pierre; the east side is served by a forest path linking south the Petit-lac-Batiscan path which runs along Perron stream.

The surface of Lac Grandbois is usually frozen from the beginning of December to the end of March, however the safe circulation on the ice is generally made from mid-December to mid-March.

He gets his supplies from: The mouth of Lac Grandbois is located at the bottom of a small bay on the southeast shore.

From there, the current flows on: The toponym "Lac Grandbois" was officialized on December 5, 1968, at the Place Names Bank of the Commission de toponymie du Québec.