The Skookumchuck River is a 45-mile (72 km) long river located in southwest Washington, United States. It is a tributary of the Chehalis River, which is the largest drainage basin located entirely within the state.

The name Skookumchuck derives from Chinook Jargon: in this context, "rapids". The word skookum means "strong", and chuck means "water". The Quinault Indian Nation, by way of the 1856 Treaty of Olympia, hold fishing rights on the river. Beginning in 2021, the river is allowed to be used as a year-round water bank and is the largest in the state, allowing a draw of 28,000 acre-feet of water per year.

The river begins with several tributaries in the Snoqualmie National Forest in the foothills of the Cascade Mountains, and flows west past the town of Bucoda, Washington to its confluence with the Chehalis River near Centralia, Washington.

The Skookumchuck Dam was built in 1970, creating the 4-mile (6.4 km) long Skookumchuck Reservoir. Its primary use is to provide water for the TransAlta coal plant and is not used for local or community water needs. The dam is an earthen bank structure measuring 190 feet (57.9 m) tall and spans 1,340 feet (408.4 m).

With low water levels in the reservoir, the system provides some flood protection to communities downstream, such as Bucoda, however, the dam was not built for flood prevention. The earthen dam has been part of several flood mitigation proposals to protect the Centralia and Chehalis communities from continuing overflow events. The embankment contains a trap system in which mature steelhead are caught and transported over the spillway but existing fish passages prevent young salmon from migrating.

The dam and reservoir is overseen by TransAlta and, by contract, will continue in their oversight role after the coal plant is closed at the end of 2025. At that time, water rights will revert to the city of Centralia for public consumption.

A 2022 study to remove the dam by the Office of Chehalis Basin (OCB) estimated a cost up to $35 million, with a potential high of $80 million when factors are added for the loss of downstream water rights. The study concluded the best options were improvements to the dam to include fish passages, as well as to use the dam for flood control purposes.

In June 2024, a petition to remove the dam at the termination of the Centralia Steam Generation Plant operations was filed by the Quinault Indian Nation. Requesting the removal by at least the end of 2025, the Quinault expects immediate, natural restoration of the river's flow and salmon habitat.

• Flood history in Chehalis, Washington
• List of Chinook Jargon placenames
• List of Washington rivers

• National Oceanic and Atmospheric Administration (NOAA) - Skookumcuck River gauge - Centralia
• United States Geological Survey (USGS) - Skookumchuck River gauge - Bucoda