Kopachuck State Park, Marine park in Gig Harbor, United States

Kopachuck State Park is a marine park along Henderson Bay in Washington that spans about 109 acres with over 5,600 feet of saltwater shoreline. The grounds feature beaches, forest areas, and walking trails with views toward the water.

The Squaxin Island, Puyallup and Nisqually tribes used the Henderson Bay area for seasonal fishing and clam gatherings. The park was logged at the start of the 20th century, leaving the second-growth forest seen today. Washington State Parks first leased the land in 1955 and opened it to the public in 1960; the name was chosen in 1958.

The name comes from Chinook Jargon trade language, where Kopa means 'at' and chuck translates to 'water'. This linguistic blend reflects the trading connections and language heritage of the coastal area.

The beach is steep and rocky but turns into a level sandbar at low tide, so time a visit to the tide tables. The park has 16 sheltered and 76 unsheltered picnic tables, kitchen shelters and two miles of hiking trails. The campground is permanently closed, and Cutts Island is reached only by boat.

Cutts Island, about half a mile offshore and reachable only by boat, is known locally as "Deadman's Island." Both the park and the island are administered by the Washington State Parks and Recreation Commission.