Sunbury-on-Thames, commonly referred to as Sunbury, is a town located in the Borough of Spelthorne in Surrey, England. It sits on the north bank of the River Thames, approximately 13 miles (21 km) southwest of central London. The town adjoins Feltham to the north, Hampton to the east, Ashford to the northwest, and Shepperton to the southwest, while Walton-on-Thames lies directly across the river to the south.
Historically, Sunbury and its surrounding towns were part of the county of Middlesex. In 1965, these areas were originally intended to become part of the newly established county of Greater London; however, they were ultimately transferred to Surrey instead.