State Route 261 (SR 261) is a 62.71-mile-long (100.92 km) state highway in the U.S. state of Washington. Serving Columbia, Franklin, and Adams counties, the highway begins at U.S. Route 12 (US 12) east of Starbuck and becomes concurrent with SR 260 from Kahlotus to SR 26 in Washtucna before ending at Interstate 90 (I-90) and US 395 in Ritzville. The highway has been legislated since 1937 from Ritzville to Washtucna as Secondary State Highway 11E (SSH 11E) and in 1957 from Washtucna to the Starbuck area as a branch of SSH 11B. The two secondary highways became SR 261 during the 1964 highway renumbering, and a gap between Washtucna and Starbuck was not paved until the construction of the Snake River Bridge was completed in 1968.

U.S. Route 12 is a major east–west U.S. Highway, running from Aberdeen, Washington, to Detroit, Michigan. It spans 430.5 miles (692.8 km) across the state of Washington, making it the second longest highway in the state. It is also the only numbered highway to span the entire state from west to east, starting near the Pacific Ocean, and crossing the Idaho state line near Clarkston. It crosses the Cascade Range over White Pass, south of Mount Rainier National Park. Portions of it are concurrent with Interstate 5 (I-5) and Interstate 82 (I-82), although the majority of the route does not parallel any interstate highway.