Nahanni National Park, National park, southwestern Northwest Territories, Canada. Established in 1972, it occupies an area of 1,177,700 acres (476,968 hectares). Its central feature is the South Nahanni River, a tributary of the Liard River; it flows southeast from the Mackenzie Mountains and is 350 mi (563 km) long. The park also contains three large canyons and a variety of birds, wildlife, and flowers.