The Mackenzie River (French: Fleuve Mackenzie) originates in Great Slave Lake, in the Northwest Territories, an flows north into the Arctic Ocean. It is the longest river in Canada at 1,738 km and, together with its headstreams the Peace and the Finlay, the second longest river in North America at 4,241 km in length. The Mackenzie and its tributaries drain 1,805,200 square kilometers. Its mean discharge is 9,700 cubic metres per second.