Thelon River, 904 km long, issues from Lynx Lake, east of Great Slave Lake, NWT. It has a drainage basin of 142 400 km2 - third among rivers flowing into Hudson Bay - and a mean discharge of 840 m3/second. It flows north and then east across the Barren Lands of the territory of Nunavut, through Beverly, Aberdeen, Schultz and Baker lakes and empties into Chesterfield Inlet, on Hudson Bay. Its main tributaries are the Dubawnt River, flowing north from Dubawnt Lake, and the Kazan River, draining numerous lakes to the southwest. The area was the haunt of the Kivallirmiut (Caribou Inuit) until the herds were depleted. Joseph Tyrell and his brother James Tyrell examined the river in 1893-94. The Thelon Game Sanctuary (38 850 km2) was established in 1927 to protect the endangered muskox. In 1990 the river was designated as part of the Canadian Heritage River System.