The Trois Saumons River (in French: Rivière Trois Saumons) is a tributary of the south shore of the St. Lawrence River where it flows to the southwest of the village of Saint-Jean-Port-Joli and to the north-east of the village of L'Islet-sur-Mer.

The Trois-Saumons river water mill in Saint-Jean-Port-Joli is located upstream of route 132.

This recreational and tourist-oriented lake, with a significant density of chalets on its banks, is surrounded by forest.

[1] From its source, the Trois Saumons River flows over 17.0 kilometres (10.6 mi), divided into the following segments: At the end of its course, the Trois Saumons River flows onto the long shore (at low tide) in the Anse de Trois-Saumons, on the south shore of the middle estuary of the St. Laurent.

[1] The toponym Rivière Trois Saumons was formalized on December 5, 1968, at the Commission de toponymie du Québec.