The Mackenzie River is the largest river in Canada, stretching over 4, 241 km from the Great Slave Lake in the Northwest Territories to the Arctic Ocean. It is the longest river system in Canada and the 11th longest in the world. The Mackenzie River is also the largest river in North America that flows into the Arctic Ocean. It is an important source of freshwater for many communities in the region, and its tributaries are home to a variety of fish species.