The lac Berthiaume (English: Berthiaume lake) is a freshwater body crossed by the Métascouac River, in the unorganized territory of Lac-Jacques-Cartier, in the La Côte-de-Beaupré Regional County Municipality, in the administrative region of Capitale-Nationale, in the province from Quebec, to Canada.

Some secondary forest roads serve this area for forestry and recreational tourism activities.

The surface of Berthiaume Lake is usually frozen from the beginning of December to the end of March, however the safe circulation on the ice is generally done from mid-December to mid-March.

A kilometer-long strait (width: between 100 and 200 meters) separates the northern and southern parts of the lake.

On the east side of Lac Berthiaume, a strip of 4.0 km (2.5 mi) (north–south direction) separates it from Métascouac Lake.