Mackenzie River Mackenzie River The Mackenzie River (Slavey language: Deh-Cho , "big river" or Inuvialuktun: Kuukpak , "great river"; ) is the longest river system in Canada, and has the second largest drainage basin of any North American river after the Mississippi River. The Mackenzie River flows through a vast, thinly populated region of forest and tundra entirely within the Canadian Northwest Territories, although its many tributaries reach into four other Canadian provinces and territories. The river's main stem is long, flowing north-northwest from Great Slave Lake into the Arctic Ocean, where it forms a large delta at its mouth. Its extensive
Geikie River (Saskatchewan) Fond du Lac River which flows out of the lake to the north-west where it drains into Lake Athabasca which ultimately drains into the Arctic Ocean via the Mackenzie River system, or into the Cochrane River which flows out of the north-eastern side of the lake and into Reindeer Lake which drains via the Churchill River system into Hudson Bay. If Hudson Bay is defined as part of the Atlantic Ocean then the Geikie River is the largest river in the world that drains naturally into two oceans. The Geikie River is bridged by Highway 905 at the highway's 184