Coteau-du-Lac is a small town in southwestern Quebec, Canada. It is on the north shore of the St. Lawrence River in the Vaudreuil-Soulanges Regional County Municipality. The name of the town comes from the old French word Coteau which meant "cluster of homes" and from its location on the north shore of Lake Saint Francis. The National historic site of the Coteau-du-Lac canal is the location of the first canal lock system in North America. The city has an industrial park.