Chehalis River is a river, as well as a river system, located wholly within the state of Washington in the United States. The Chehalis River has a 2,660 square-mile (6,840 square-km) drainage basin, located between Aberdeen, Washington and the Willapa Hills. This includes the entire Chehalis River watershed but not the Grays Harbor estuary. The river is roughly 108.2 miles (175.29 km) in total length, not counting tributaries.
The Chehalis River is the largest river system located entirely within Washington state. Only the Columbia River, located between Washington and Oregon, is larger.
