The Selwyn Mountains are a mountain range in northern Canada, forming part of the border between the Yukon Territory and the Northwest Territories, and which are part of the Eastern System of the Canadian Cordillera (aka the Western Cordillera). They are neighboured on the east by the Mackenzie Mountains and on their northwest end by the Brooks Range. To their southwest is the Yukon Plateau, while a lower southward extension of their mountain spine protrudes into British Columbia as the Liard Plateau. In some reckonings the Selwyns and Mackenzies are considered to be part of the Rocky Mountains, but that range officially lies only to the south of the Liard River and the aforesaid plateau.