This largest tributary of the Athabasca from the east is so named from the contrast of its water with that of the muddy Athabasca. It was part of the famous route to the Athabasca via Methy Portage (now in Saskatchewan), and has been referred to by a number of names. Fur trader Peter Pond first travelled the Clearwater River in 1778 in his exploration of the Athabasca country and in 1787 shows it as the Pelican River. David Thompson, in 1798, recorded its name as the Lesser Athabasca River. Philip Turnor, surveyor for the Hudson's Bay Company, noted in his journal for Monday May 14, 1792: "Put up near the old Canadian House below the mouth of the Wash-a-cum-mow seepe or clear water river...." The name Wa-se-ka-mew-see pee which means "clear water," is apparently in current usage among local residents.

Flows west into Athabasca River at Fort McMurray.