The Lake Bécancour is a lake located in the municipality of Thetford Mines in the administrative region of Chaudière-Appalaches, in Quebec, in Canada. It is the source of the Bécancour River, which flows through the Centre-du-Québec administrative region and joins the St. Lawrence River.

Its area is approximately 0.973 kilometres (0.60 mi), its altitude of 335 metres (1,099 ft) and its maximum depth is 3.4 meters (11 ft).

The toponym "lac Bécancour" was made official on December 5, 1968, at the Commission de toponymie du Québec.