The Inconnue River (in French: rivière Inconnue) flows in the municipalities of Cap-Saint-Ignace and Notre-Dame-du-Rosaire, in the Montmagny Regional County Municipality, in the administrative region of Chaudière-Appalaches, in Quebec, in Canada.

The "Inconnue River" is a tributary of the east bank of the rivière des Perdrix, which flows towards the south bank of the Bras Saint-Nicolas; from there, the current flows to the southeast shore of the rivière du Sud (Montmagny); the latter flows north-east to the south shore of the St. Lawrence River.

[1] The main neighboring watersheds of the Inconnue River are: The Inconnue River has its source on the north slope of the Notre Dame Mountains, in the township of Bourdages, in the municipality of Cap-Saint-Ignace.

Several branches of mountain and forest streams feed the head of the Inconnue River.

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