Lac Martin-Valin is a freshwater body of the watershed of bras des Canots, located on the north shore of the St. Lawrence River, in the unorganized territory of Mont-Valin, in the Le Fjord-du-Saguenay Regional County Municipality, in the administrative region of the Saguenay-Lac-Saint-Jean, in the province of Quebec, Canada.

The area of Lake Martin-Valin is included in the territory of Monts-Valin National Park.

Several secondary forest roads serve the bays and the surroundings of Lake Martin-Valin for the needs of recreational tourism activities.

[1] The mouth of Lake Martin-Valin is located at: From the mouth of Lake Martin-Valin, the current follows the course of the arms of the Canots on 12.7 kilometres (7.9 mi) first towards the Southwest, to flow on the North bank of the Valin River.

The toponym "Lac Martin-Valin" was formalized on February 12, 1987, by the Commission de toponymie du Québec.