The Willapa River is a river on the Pacific coast of southwestern Washington in the United States, approximately 20 miles (32 km) long. It drains an area of low hills and a coastal plain into Willapa Bay, a large estuary north of the mouth of the Columbia River.
The river rises in the Willapa Hills in southeastern Pacific County, approximately 25 miles (40 km) west of Chehalis. It flows northwest in a winding course past the small communities of Willapa and Raymond. It enters the northwest end of Willapa Bay at South Bend.