Vashon is a census-designated place (CDP) in King County, Washington, United States. It covers an island alternately called Vashon Island or Vashon–Maury Island, the largest island in Puget Sound south of Admiralty Inlet. The population was 11,055 at 2020, up from 10,624 at the 2010 census and the size is 36.9 square miles (95.6 km2).

King County is located in the U.S. state of Washington. The population was 2,269,675 in the 2020 census, making it the most populous county in Washington, and the 12th-most populous in the United States. The county seat is Seattle, also the state's most populous city.