river in northern Yukon Territory and northwestern Mackenzie District of the Northwest Territories, Canada, the northernmost tributary of the Mackenzie River. From its major headstream, the Ogilvie River, in the mountains of central Yukon Territory, the river flows generally northeastward for 425 mi (684 km) to join the Mackenzie near Fort McPherson, a fur-trading post and the only significant riverine settlement at the northern end of the Peel River Game Reserve. Its upper course through Peel Plateau is characterized by canyons as deep as 1,000 ft (300 m); its lower valley, much of which consists of nature preserve and game sanctuary, is wide, with braided channels, gravel bars, and small wooded islands. The river was named for Sir Robert Peel (Peel, Sir Robert, 2nd Baronet), the 19th-century British prime minister.