The rivière du Milieu (English: river of the middle) is a tributary of Poutrincourt Lake, flowing into the unorganized territory of Lac-Ashuapmushuan, Quebec, into the Regional County Municipality (RCM) of Le Domaine-du-Roy, in the administrative region of Saguenay-Lac-Saint-Jean, Quebec, Canada.

This last road connects to the Northeast at route 167 linking Chibougamau and Saint-Félicien, Quebec.

The surface of the Milieu River is usually frozen from early November to mid-May, however, safe ice circulation is generally from mid-November to mid-April.

The Milieu River originates at the mouth of Frontenac Lake (Milieu River) (length: 6.6 kilometres (4.1 mi); width: 1.9 kilometres (1.2 mi); altitude: 427 metres (1,401 ft)) located in Buade Township.

The mouth of this head lake is located at: From the mouth of Frontenac Lake (Milieu River), the Milieu River flows over 17.8 kilometres (11.1 mi) through marsh areas, according to the following segments: The confluence of the Milieu River with the Poutrincourt Lake is located at: The Milieu River flows to the bottom of a bay on the south shore of the eastern part of Poutrincourt Lake (length: 19.7 kilometres (12.2 mi); maximum width: 6.7 kilometres (4.2 mi); altitude: 392 metres (1,286 ft)).