King County is a county in the U.S. state of Washington. The population was 2,188,649 in the 2017 census estimate. King is the most populous county in Washington. The county seat is Seattle, which is the state's largest city.
King County is one of three Washington counties that are included in the Seattle–Tacoma–Bellevue metropolitan statistical area. About two-thirds of King County's population lives in Seattle's suburbs.