Rivière-Mouchalagane is an unorganized territory in the Côte-Nord region of Quebec, Canada, part of Caniapiscau Regional County Municipality. The ghost town of Gagnon is located in the territory along Quebec Route 389 which also provides access to Fermont and Labrador City. The eponymous Mouchalagane River has its source in Sommet and Itomamis Lakes, and flows for 132 kilometres (82 mi) to the south, after which it drains into the Manicouagan Reservoir. Before the formation of this reservoir, the river would flow into Lake Mouchalagane.