Westchester County is a suburban county with about 940,000 residents located in the U.S. state of New York. It is part of the New York Metropolitan Area. It was named after Chester, in England. The county seat is White Plains.

Westchester County was an original county of the Province of New York, one of twelve created in 1683. At the time, it also included the present Bronx County, which constituted the Town of Westchester and portions of three other towns: Yonkers, Eastchester, and Pelham. In 1846, a new town, West Farms, was created by secession from Westchester; in turn, in 1855, the Town of Morrisania seceded from West Farms. In 1873, the Town of Kingsbridge seceded from Yonkers.