river in Nord-du-Québec region, northeastern Quebec province, Canada. It rises near the Labrador (Newfoundland) border, flows northward parallel to the boundary for 350 miles (563 km), and empties into the eastern side of Ungava Bay. Named after King George III by Moravian missionaries in 1811, the river flows mostly through a treeless tundra in a course broken by numerous falls and rapids. At its mouth is Kangiqsualujjuaq, established in 1838 as a Hudson's Bay Company trading post.