River, western central Canada.
A tributary of the Mackenzie River in Alberta, it rises in the Rocky Mountains in Jasper National Park , and flows northeast and north 765 mi (1,231 km) into Lake Athabasca . Its chief tributaries are the Pembina, Lesser Slave, and La Biche rivers. Extensive petroleum deposits lie in oil-impregnated sands (Athabasca Tar Sands) along a 70-mi (113-km) stretch of the river.