State Route 107 (SR 107) is a 7.93-mile-long (12.76 km) state highway serving Grays Harbor County in the U.S. state of Washington. The highway travels northeast from U.S. Route 101 (US 101) south of Cosmopolis to an interchange with US 12 in Montesano. SR 107 was created during the 1964 highway renumbering as the successor to a branch of Primary State Highway 9 (PSH 9), established earlier in 1937.