Churchill (river, central Canada), river of central Canada, 1,600 km (1,000 mi) long. It begins at Lac La Loche in northwestern Saskatchewan and flows east through several lakes in northern Saskatchewan and Manitoba before emptying into Hudson Bay. Hydroelectric plants on the river provide power for the mining industry of northern Manitoba. The river was once a major route for fur traders. It was originally called Missinipi, a native word for “big river.” In the 1780s, it was renamed in honor of John Churchill, 1st Duke of Marlborough, who was governor of the Hudson's Bay Company from 1685 to 1691.