Sudley is a census-designated place in Prince William County, Virginia, United States. As of the 2010 census, Sudley comprises what in the 2000 census were the Sudley and West Gate CDPs. Sudley's population including West Gate was 16,203 at the 2010 census, and excluding West Gate was 7,719 at the 2000 census. Sudley contains the Splash Down Waterpark. Residents of Sudley are represented in the Virginia House of Delegates by Danica Roem.