The London Borough of Croydon () is a London borough in south London, part of Outer London. It covers an area of . It is the southernmost borough of London. At its centre is the historic town of Croydon from which the borough takes its name; while other urban centres include Coulsdon, Purley, South Norwood, Norbury, New Addington, Selsdon and Thornton Heath. Croydon is mentioned in Domesday Book, and from a small market town has expanded into one of the most populous areas on the fringe of London. The borough is now one of London's leading business, financial and cultural centres, and its influence in entertainment and the arts contribute to its status as a major metropolitan centre. Its population is 390,719, making it the largest London borough and sixteenth largest English district.
The borough was formed in 1965 from the merger of the County Borough of Croydon with Coulsdon and Purley Urban District, both of which had been within Surrey. The local authority, Croydon London Borou