The Sauvage River flows through the municipalities of Lemieux (MRC Bécancour Regional County Municipality), Saint-Louis-de-Blandford (MRC Arthabaska Regional County Municipality), Maddington Falls (MRC Arthabaska Regional County Municipality), Saint-Sylvère (MRC Bécancour Regional County Municipality), Sainte-Marie-de-Blandford (MRC Bécancour Regional County Municipality).

The main neighboring hydrographic slopes of the Sauvage River are: The Sauvage River has its source in a marsh area in the southern part of the municipality of Lemieux.

This headland is located 2.7 kilometres (1.7 mi) northwest of highway 20, 3.0 kilometres (1.9 mi) southeast of the village of Lemieux and west of the village of Saint-Louis-de-Blandford as well as 0.8 kilometres (0.50 mi) from the inter-MRC limit of Bécancour Regional County Municipality) and Arthabaska.

From its head zone, the Sauvage River flows for 11.4 kilometres (7.1 mi), in a forest and agricultural zone, with a drop of 20 metres (66 ft), divided into the following segments: The Sauvage River empties on the south bank of the Gentilly River.

The toponym "rivière Sauvage" was made official on August 18, 1978, at the Commission de toponymie du Québec.