The Stewart River is a 533-kilometre (331 mi) tributary of Yukon River in the Yukon Territory of Canada. It originates in the Selwyn Mountains, which stand on the border between the Northwest Territories and the Yukon Territory. From there, the Stewart flows west, past the village of Mayo. The river is crossed by the Klondike Highway at the village of Stewart Crossing, and the highway parallels the river westward for about 56 kilometres (35 mi). After leaving the highway, the river travels southwest until it intersects the Yukon River 112 kilometres (70 mi) south of Dawson City.