The rivière aux Plats (English: Flat River) is a tributary of the Gulf of St. Lawrence, flowing in the municipality of L'Île-d'Anticosti, in the Minganie Regional County Municipality, in the administrative region of North Shore, in province of Quebec, in Canada.

This valley is served by a network of forest roads for forestry and recreational tourism activities.

[1][2] The Rivière aux Plats draws its source from a mountain stream (altitude: 260 m (850 ft)), located in the center-south of the island, just south of the forest road (east–west direction).

This source is located in a forest area at: From its source, the Rivière aux Plats descends between the Chicotte River (located on the west side) and the Pavillon River (east side).

The Rivière aux Plats generally flows south-east, then south, over 26.2 km (16.3 mi) with a drop of 259 m (850 ft), according to the following segments: The Rivière aux Plats drains into a small bay on the south shore of Anticosti Island, in the Gulf of St. Lawrence, on the west side of Cap des Caps.