One Canada Square is a skyscraper in Canary Wharf, London. It is the third tallest building in the United Kingdom at 770 feet (235 m) above ground level, and contains 50 storeys. It achieved the title of the tallest building in the UK upon completion in 1991 and held the title for 21 years until the completion of The Shard (310m) in 2012.

Canary Wharf is an area of London, England, located near the Isle of Dogs in the London Borough of Tower Hamlets. Canary Wharf is defined by the Greater London Authority as being part of London's central business district, alongside Central London. Alongside the City of London, it constitutes one of the main financial centres in the United Kingdom and the world, containing many high-rise buildings including the third-tallest in the UK, One Canada Square, which opened on 26 August 1991.