Churchill (river, northeastern Canada), river of Newfoundland and Labrador, Canada, 335 km (208 mi) long. It begins at Ashuanipi Lake in western Labrador and flows north over the rugged Labrador Plateau. It then turns southeast, leaving the plateau near Churchill Falls and finally emptying into Lake Melville, a saltwater lake linked to the Atlantic Ocean. One of Canada's largest hydroelectric projects is on the river at Churchill Falls. This dam created the Smallwood Reservoir, a large body of water along the river's course. The river was known as the Hamilton River from 1821 until 1965, when it was renamed for the British prime minister Sir Winston Churchill.