River, western Canada.
Formed by the confluence of the Finlay and Parsnip rivers in the Canadian Rockies of British Columbia, it flows east across the border of Alberta to join the Slave River just north of its outlet from Lake Athabasca . It is 1,195 mi (1,923 km) long. It was explored by Alexander Mackenzie in 179293 and became a major fur-trading route. It is an important source of hydroelectric power.