State Route 8 (SR 8) is a state highway in Grays Harbor and Thurston counties, of the U.S. state of Washington. It extends 20.67 miles (33.27 km) from U.S. Route 12 (US 12) in the city of Elma, east to an interchange with US 101 about 5.90 miles (9.50 km) northwest of the state capital, Olympia. SR 8 intersects SR 108 west of McCleary. The route connects Elma and Olympia as part of a corridor between Aberdeen and the Puget Sound region.

Grays Harbor County is a county in the U.S. state of Washington. As of the 2020 census, the population was 75,636. Its county seat is Montesano, and its largest city is Aberdeen. Grays Harbor County is included in the Aberdeen Micropolitan Statistical Area.