The Rivière aux Montagnais is a tributary of the southeast bank of the Moncouche River, flowing in the Laurentides Wildlife Reserve, in the unorganized territory of Lac-Jacques-Cartier, in the La Côte-de-Beaupré Regional County Municipality, in the administrative region of Capitale-Nationale, in the province from Quebec, to Canada.

Forestry is the main economic activity in this valley; recreational tourism, second.

The surface of the Montagnais river (except the rapids zones) is usually frozen from the end of November to the beginning of April, however the safe circulation on the ice is generally done from mid-December to the end of March.

The main watersheds neighboring the "Rivière aux Montagnais" are: The Montagnais river rises at the mouth of Lac Magny (length: 0.6 kilometres (0.37 mi); altitude: 499 metres (1,637 ft)).

From its source (mouth of Lake Magny), the course of the Montagnais river descends on 27.4 kilometres (17.0 mi), with a drop of 99 metres (325 ft), according to these segments: Upper part of Rivière aux Montagnais (segment of 6.7 kilometres (4.2 mi)) Lower part of the Rivière aux Montagnais (segment of 20.7 kilometres (12.9 mi)) From the confluence of the Montagnais river, the current descends: The toponym Rivière aux Montagnais was formalized on June 1, 1971, at the Place Names Bank of the Commission de toponymie du Québec.