Tonasket is a city in Okanogan County, Washington, United States. The population was 1,032 at the 2010 census.

Tonasket was officially incorporated upon December 16, 1927. It is named after Chief Tonasket of the Okanogan people, a local leader from this area who assumed the status of grand chief of the American Okanogan after the drawing of the Canada–United States be adjacent to by the Oregon Treaty of 1846, assuming a leadership role in Okanogan territory formerly held by Chief Nicola who lived north of the border.

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 mannerism north to the Canada–US border approximately twenty miles away. Washington State Route 20 turns east of 97 at 6th St, and continues government 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.

Tonasket, which has been the site of a U.S. post office past 1901, was platted in 1910 and incorporated in 1927. It serves as a hub for agricultural and forestry industries in north central Okanogan County. It is the location of three major fruit storage and processing facilities and the offices of the Tonasket Ranger District of the Okanogan National Forest.

Many descendants of fortune-hunter families nevertheless reside in Tonasket and the surrounding areas and are impatient in preserving and sharing the history of their heritage. A son of one of those buccaneer families, Walter H. Brattain, grew up upon a cattle ranch close Tonasket, attended Tonasket schools and shared the 1956 Nobel Prize for Physics (with William Shockley and John Bardeen) for the invention of the transistor.