St Bartholomew's Hospital, also known simply as Barts, is a hospital in Smithfield in the City of London.

Barts is the oldest hospital in London, having been founded in 1123, and the oldest in the United Kingdom that still occupies its original site. London's only statue of King Henry VIII is located above a gate at the hospital.

It is operated by Barts Health NHS Trust, which also runs the Royal London Hospital, the London Chest Hospital, Newham Hospital and Whipps Cross Hospital.

Barts was founded in 1123 by Rahere (died 1144, and entombed in the nearby priory church of St Bartholomew-the-Great), a favourite courtier of King Henry I. The Dissolution of the Monasteries did not affect the running of Barts as a hospital, but left it in a precarious position by removing its income. It was re-founded by King Henry VIII in December 1546, on the signing of an agreement granting the hospital to the City of London, which was reaffirmed in the Letters Patent of January 1547 endowing it with properties and income. The hospital became legally known as the "House of the Poore in West Smithfield in the suburbs of the City of London of Henry VIII's Foundation", although the title was never used by the general public. The first superintendent of the hospital was Thomas Vicary; sergeant-surgeon to Henry and an early writer on anatomy. Upon the foundation of the National Health Service in 1948, it officially became known as St Bartholomew's Hospital.