Frontenac Lake is a freshwater body of the Lac-Ashuapmushuan, Quebec unorganized territory in the northwestern part of the Regional County Municipality (RCM) Le Domaine-du-Roy in the region of Saguenay-Lac-Saint-Jean, in the province of Quebec, in Canada.

This last road connects to the Northeast at route 167 linking Chibougamau and Saint-Félicien, Quebec.

The surface of Lake Frontenac is usually frozen from early November to mid-May, however, safe ice circulation is generally from mid-November to mid-April.

The mouth of Lake Frontenac is located at: The main hydrographic slopes adjacent to Lake Frontenac are: The Maskoskanaw River empties into a bay on the east shore of Lake Frontenac, which runs through the North 4.4 kilometres (2.7 mi) to its mouth.

From there, the current flows down the Milieu River (Normandin River) on the north, to the south shore of the Poutrincourt Lake, which the current crosses on 15.4 kilometres (9.6 mi) to the North.