St Swithun's School is an independent day, weekly and full-boarding school for girls in Winchester, Hampshire. It is named after Saint Swithun, a Bishop of Winchester and patron saint of Winchester Cathedral.

Winchester is a cathedral city in Hampshire, England. The city lies at the heart of the wider City of Winchester, a local government district, at the western end of the South Downs National Park, on the River Itchen. It is 60 miles (97 km) south-west of London and 14 miles (23 km) from Southampton, its nearest city. At the 2021 census, the built-up area of Winchester had a population of 48,478. The wider City of Winchester district includes towns such as Alresford and Bishop's Waltham and had a population of 127,439 in 2021. Winchester is the county town of Hampshire and contains the head offices of Hampshire County Council.