Squaxin Island is in the extreme southwestern part of Puget Sound in Mason County, Washington, United States. The island is an Indian reservation of the Native American Squaxin Island Tribe. It once contained a Washington State Park by the same name, which has since been closed, and the land returned to the Squaxin Tribe. The island's land area is 5.739 km2 (2.216 sq mi). There was no resident population as of the 2000 census.
Squaxin Island is separated from Harstine Island, to the east, by Peale Passage.
The island's name comes from the Lushootseed placename swwáxsəd.
Coordinates: 47°11′51″N 122°54′43″W / 47.1974°N 122.9119°W