The Lac Ouiatchouan (old appellation: Lac Ouiatchouane) is a body of fresh water located in ranges V and V1, in the municipality of Lac-Bouchette, in the MRC Le Domaine-du-Roy Regional County Municipality, in the administrative region Saguenay–Lac-Saint-Jean, in the province of Quebec, in Canada.

This lake located in the heart of the village of Lac-Bouchette is characterized by recreational and tourist activities, in an agricultural and forestry environment.

A narrow 0.5 km isthmus which is crossed on the west side by a channel of about 250 m long designated the "Pass", separates the lakes Bouchette and Ouiatchouane.

The Qui-Mène-du-Train river flows on the eastern shore of Lake Ouiatchouan, in the heart of the village of Lac-Bouchette.

This toponym was registered on September 5, 1985, at the Place Names Bank of the Commission de toponymie du Québec.