Lake Saint-Louis is a lake in southwestern Quebec, Canada, at the confluence of the Saint Lawrence and Ottawa Rivers. The Saint Lawrence Seaway passes through the lake.
Lake St. Louis is a widening of the St. Lawrence River in the Hochelaga Archipelago. It is also fed by the Ottawa River via the Lake of Two Mountains at Sainte-Anne-de-Bellevue, the Beauharnois Canal, the Soulanges Canal, the St. Louis River, and the Châteauguay River.
The lake is bounded to the north and east by the Island of Montreal, by Beauharnois-Salaberry, Roussillon, and Vaudreuil-Soulanges. The town of Beauharnois with its power-dam and canal lie to the south.
The West Island shore is mostly built-up with private houses, but includes some parks and clubs such as the Pointe-Claire Canoe Club, and the Pointe-Claire Yacht Club.