Lac Sacacomie, Natural lake in Saint-Alexis-des-Monts, Canada.

Lac Sacacomie is a freshwater lake in Saint-Alexis-des-Monts, about 35 km west of Shawinigan. It has the shape of two rectangles set end to end north-south, separated by two large peninsulas pointing toward Grosse Île in the centre. Three smaller islands emerge, and five deep bays indent the shores, three on the north side and two on the south.

Pehr Kalm recorded the name as "Saghackhomi" in his 1749 travel journal through Canada. The spelling was formalized in the 1870 survey minutes of the De Calonne township by surveyor Télesphore Chavigny de La Chevrotière. The toponym was officially registered at the Quebec Toponymy Commission on 5 December 1968.

The name Sacacomie appears as "Saghackhomi" in the 1749 travel journal of Swedish naturalist Pehr Kalm. He recorded that French settlers gathered a plant they called sagackomi and mixed it with tobacco, a practice he considered harmful to the lungs. The Abenaki knew the lake as Sagakhimen, from their word for blueberry.

The lake drains east through the Sacacomie river toward Saint-Alexis-des-Monts, where it joins the rivière du Loup. Access is from the village, 35 km west of Shawinigan; the shoreline is mostly mixed forest with few inhabitants. The lake lies 271 m above sea level and covers 9.3 km², stretching 6.2 km north-south and 3.9 km east-west.

The water has multiple bays along different shorelines, connected to the surrounding river system through a waterway. This structure creates varied landscapes for those on the water.