It rises in several forks in northwestern Lane County, approximately 15 mi (24 km) northwest of Eugene. It flows generally WNW in a winding course through the mountains of southern Benton and Lincoln counties, past Alsea and Tidewater, passing through the Siuslaw National Forest. It enters the Pacific at Alsea Bay, a wide estuary at Waldport
The Alsea is one of the most pristine estuaries on the Oregon Coast, and offers excellent opportunities for recreation.
Follow the tide up the river to forested campgrounds and sunny swimming holes.
Located on the waterfront just upriver from the mouth of Alsea Bay, the Port's public facilities include a launch ramp, boat moorage, great beach access and picnic area.