Sunbury-on-Thames (or commonly Sunbury) is a suburban town on the north bank of the River Thames in the Borough of Spelthorne, Surrey, centred 13 mi (21 km) southwest of central London. Historically part of the county of Middlesex, in 1965 Sunbury and other surrounding towns were initially intended to form part of the newly created county of Greater London but were instead transferred to Surrey. Sunbury adjoins Feltham to the north, Hampton to the east, Ashford to the northwest and Shepperton to the southwest. Walton-on-Thames is to the south, on the opposite bank of the Thames.

The town has two main focal points: Lower Sunbury (known locally as Sunbury Village) is the older part, adjoining the river. Sunbury Common (known locally as Sunbury Cross) is to the north and surrounds the railway station and the London end of the M3 motorway. Lower Sunbury contains most of the town’s parks, pubs and listed buildings, whereas Sunbury Common is more urban and includes offices and hotels. Lower Sunbury holds an annual fair and regatta each August.

Sunbury railway station is on the Shepperton branch line. Trains to and from London Waterloo are operated by South Western Railway.