State Route 122 (SR 122) is a 7.88-mile-long (12.68 km) state highway on the north shore of Mayfield Lake in rural Lewis County, located within the U.S. state of Washington. The highway begins at U.S. Route 12 (US 12) in Silver Creek and travels east through Ike Kinswa State Park before turning south over the Cowlitz River to Mossyrock, ending at US 12. SR 122 was established in 1991 on roads built in the 1910s and 1940s and the designation was transferred from SR 142.