Tonasket is a city located along the eastern bank of the Okanogan River in north-central Okanogan County, Washington. U.S. Highway 97, the main north–south highway through central Washington, bisects the city on its way north to the Canada–US border approximately twenty miles away. Washington State Route 20 turns east of 97 at 6th St, and continues running across the state. The city is bordered on the north by Siwash Creek, on the south by Bonaparte Creek, and on the west by the Okanogan River.