Dolphin Square is a prominent estate of private flats near the River Thames in Pimlico, Westminster. Built between 1935 and 1937, it was, until the development of Highbury Square, the largest garden square in Greater London constructed as private housing.

Its 1,234 flats were described by Sir Nikolaus Pevsner as the "largest self-contained block of flats in Europe". The design influenced later municipal housing developments. At the time of its completion, Dolphin Square was described as "London's most distinguished address".

The estate comprises 13 blocks named after famous navigators and admirals and features a range of amenities including a swimming pool, tennis courts, café and wine bar, gym, shopping arcade, and landscaped gardens. The Grade II listed 3.5-acre gardens were designed by Richard Sudell and reflect global horticultural styles.

Situated near the Houses of Parliament, Dolphin Square has housed a range of prominent residents, including former Prime Minister Harold Wilson, as well as notable figures from the arts, culture, and even the royal family.

Dolphin Square is located in Pimlico, London, within the City of Westminster. It is bounded by Grosvenor Road, Chichester Street, Claverton Street, and St George's Square, near the River Thames. The estate is close to Pimlico Underground station and within walking distance of Tate Britain and the Houses of Parliament.

Dolphin Square is on the site of the former works of the developer and builder Thomas Cubitt who created the surrounding Pimlico district in the 19th century. The Royal Army Clothing Depot was built on the site after Cubitt's death and stood until 1933 when the leasehold on the site reverted to the Duke of Westminster. An American firm, the Fred F. French Companies, bought the freehold for the site from the Duke with plans to build a large residential development, provisionally named Ormonde Court. Although the planning stage was successfully concluded with the LCC by January 1935, French still needed financial backing for the enterprise. At the same time, he had over-extended his credit during his recent developments in New York City such as Tudor City and Knickerbocker Village and found himself unable to repay interest on earlier deals. Needing a new backer, French sold his obligations to Richard Costain Ltd., run by Richard Rylands Costain. New plans were drawn up by the architect S. Gordon Jeeves, and building started in September 1935. Lord Amulree formally opened the building on 25 November 1936.

A. P. Herbert, writing in Dolphin Square (a promotional booklet produced for Costains in 1935, with illustrations by H. M. Bateman) described the Square as "a city of 1,250 flats, each enjoying at the same time most of the advantages of the separate house and the big communal dwelling place". The provision of a restaurant made him fear that "fortunate wives will not have enough to do. A little drudgery is good for wives, perhaps. The Dolphin lady may be spoiled." On purchasing the site, Costain remarked to a colleague: "in two or three years we'll either drive up to this spot in a Rolls-Royce, or we'll be standing here selling matches."

In 1958, Costains sold Dolphin Square for £2.4 million to Sir Maxwell Joseph, who sold it to Lintang Investments in 1959 for £3.1 million. Westminster City Council bought the lease of the block for £4.5 million in the mid-1960s, and subsequently sub-let it to the Dolphin Square Trust, a housing association, which had been newly created for the purpose. In January 2006, the Trust and the Council sold Dolphin Square to the American Westbrook Holdings group for £200 million, and in 2020, Axa Investment Managers acquired the estate on behalf of its clients.