river, northeastern Ontario, Canada. Arising at the confluence of its two major headstreams, the Mattagami, 260 miles (420 km) long, and the Missinaibi, 265 miles long, it flows northeastward for more than 60 miles (100 km) to James Bay. Though short in length, the Moose, along with its headstreams and tributaries, including the Abitibi River (340 miles), drains most of northeastern Ontario.

Economic activities in the river's watershed include mining and pulp- and paper-milling operations powered by hydroelectric plants on the Abitibi and Mattagami rivers. The Ontario Northland Railway parallels the Abitibi valley and terminates at Moosonee, opposite the historic island of Moose Factory in the river's mouth. Tidewater Provincial Park includes several islands near Moose Factory. Kapuskasing, Iroquois Falls, and Timmins are the chief towns in the river's basin.