The Moose River is a river in the Hudson Plains ecozone of northern Ontario, Canada. The river flows 100 km northeast from the confluence of the Mattagami and Missinaibi Rivers into James Bay. Its drainage basin is 108,500 square kilometres (41,900 sq mi) and it has a mean discharge rate of 1,370 cubic metres (48,000 cu ft). Its full length is 547 kilometres (340 mi) if counted from the head of the Mattagami River.

The Southern Hudson Bay taiga is a terrestrial ecoregion, as classified by the World Wildlife Fund, which extends along the southern coast of Hudson Bay and resides within the larger taiga biome. The region is nearly coterminous with the Hudson Plain, a Level I ecoregion of North America as designated by the Commission for Environmental Cooperation (CEC) in its North American Environmental Atlas.