The Sixes River flows about 31 miles (50 km) through coastal forests in southwestern Oregon in the United States. It drains a rugged region of the Klamath Mountains along the Pacific north of Port Orford. It rises in the mountains of northern Curry County, south of in the Rogue River – Siskiyou National Forest. It flows generally west, through Grassy Knob Wilderness and the small community of Sixes, and eventually enters the Pacific just north of Cape Blanco, the westernmost point in Oregon. The mouth of the river is along the coast in Cape Blanco State Park.