State Route 166 (SR 166) is a 5.13-mile (8.26 km) long state highway serving the city of Port Orchard within Kitsap County in the U.S. state of Washington. The highway begins at an interchange with SR 16 west of Port Orchard and travels along the Sinclair Inlet to Downtown Port Orchard and ends as Mile Hill Drive at Whitter Avenue near the eastern city limits.