Mackenzie, Former administrative district, Canada. Occupying an area of 527,490 sq mi (1,366,199 sq km), it included the greater part of the northern mainland of Canada between Yukon Territory and Keewatin district, as well as most of the Mackenzie River valley, Great Bear Lake, and Great Slave Lake. Created in 1895, it was administered from Edmonton; it ceased to exist in 1979.