The London Borough of Merton (/ˈmɜːrtən/ ^ⓘ) is a London borough in London, England. The borough was formed under the London Government Act 1963 in 1965 by the merger of the Municipal Borough of Mitcham, the Municipal Borough of Wimbledon and the Merton and Morden Urban District, all, apart from Wimbledon, were formerly within Surrey.

The main commercial centres in Merton are Mitcham, Morden and Wimbledon, of which Wimbledon is the largest. Other smaller centres include Raynes Park, Colliers Wood, South Wimbledon and Wimbledon Park. The borough is the host of the Wimbledon tournament, one of tennis's Grand Slam competitions.

The borough derives its name from the historic parish of Merton which was centred on the area now known as South Wimbledon. The local authority is Merton London Borough Council, which is based in Morden.

The area of the modern borough broadly corresponds to the four ancient parishes of Merton, Mitcham, Morden, and Wimbledon, all of which were historically in the county of Surrey.

The parish of Wimbledon was made a local government district in 1866. Such districts were converted into urban districts under the Local Government Act 1894. The Wimbledon Urban District was subsequently incorporated to become the municipal borough of Wimbledon in 1905.

Merton was made an urban district in 1907, which was enlarged in 1913 to take in neighbouring Morden, becoming the Merton and Morden Urban District. Mitcham was made an urban district in 1915, which was incorporated to become the municipal borough of Mitcham in 1934.

The modern borough was created in 1965 under the London Government Act 1963, covering the combined area of the former boroughs of Mitcham and Wimbledon and the Merton and Morden Urban District. The area was transferred from Surrey to Greater London to become one of the 32 London Boroughs.

The name Merton for the borough was chosen as a compromise, following a dispute between Wimbledon and Mitcham over the new borough's name.