The Lac des Alliés (English: Allied Lake) is a freshwater body crossed west by the Rocheuse River, located in the unorganized territory of Lac-Jacques-Cartier, in the La Côte-de-Beaupré Regional County Municipality, in administrative region of Capitale-Nationale, in province of Quebec, in Canada.

The Lac des Alliés watershed is mainly served on the east side by the route 175 which links the towns of Quebec and Saguenay.

From the mouth of Lac des Alliés, the current descends consecutively on 3.8 kilometres (2.4 mi) to the west, then north following the course of the rivière Rocheuse; on 4.6 kilometres (2.9 mi) towards the southwest by following the course of the rivière du Malin; then on generally towards the south along the current of the Jacques-Cartier River to the northeast bank of the Saint-Laurent river.

[1] A dam is built at its mouth allowing a water retention height of 3.1 kilometres (1.9 mi) for a reservoir capacity of 4,273,040 metres (14,019,160.105 ft).

[3] The toponym Lac des Alliés was formalized on December 5, 1968, by the Commission de toponymie du Québec.