Island County is a county located in the U.S. state of Washington.
Island County was created out of Thurston County on December 22, 1852, by the legislature of Oregon Territory, and is the eighth-oldest county in Washington. It originally encompassed what are now Snohomish, Skagit, Whatcom, and San Juan Counties.
Island County's name reflects the fact that it is composed entirely of islands. It contains two large islands, Whidbey and Camano, and seven smaller islands (Baby, Ben Ure, Deception, Kalamut, Minor, Smith, and Strawberry).
According to the U.S. Census Bureau, the county has a total area of 517 square miles (1,340 km2), of which 208 square miles (540 km2) is land and 309 square miles (800 km2) (60%) is water. It is the second-smallest county in Washington by area.