State Route 129 (SR 129) is a state highway in Asotin County, Washington, United States. It travels north–south at the southeastern corner of the state, connecting with Oregon Route 3 (OR 3) at the Oregon state line south of Anatone. The highway then follows the Snake River, which marks the Idaho state border, north to Clarkston and terminates at U.S. Route 12 (US 12). SR 129 also has a short spur route that connects to a separate intersection with US 12 in Clarkston.