Sir Hugh Maxwell Casson (23 May 1910 – 15 August 1999) was a British architect, interior designer, artist, and influential writer and broadcaster on 20th century design. He is particularly noted for his role as director of architecture at the 1951 Festival of Britain on London's South Bank.

Casson's family originated from Wales. He was the nephew of actor, Sir Lewis Casson. Hugh Casson studied at Eastbourne College in East Sussex, then St John's College, Cambridge (1929-1931), after which he spent time at the Bartlett School of Architecture in London. Up to the start of the Second World War in 1939, he divided his time between teaching at the Cambridge School of Architecture and working in the London office of his Cambridge tutor Christopher (Kit) Nicholson . During the war, he worked in the Camouflage Service of the Air Ministry.

Hugh Casson was appointed to his role as director of the Festival in 1948 at the age of 38 and set out to celebrate peace and modernity through the appointment of other young architects. For example, the Modernist design of the Royal Festival Hall was led by a 39-year-old, Leslie Martin . Casson's Festival achievements led to him being knighted in 1952.

After the war, and alongside his Festival work, Casson went into partnership with young architect Neville Conder . Their projects included various corporate headquarters buildings, university campuses, the Elephant House at London Zoo, a building for the Royal College of Art (where Casson was Professor of Interior Design from 1955 to 1975), and the masterplanning and design of the Sidgwick Avenue arts faculty buildings for the University of Cambridge. This latter project lasted some 30 years.

As a leading light in the fine arts, Casson also served as Provost of the Royal College of Art and, after being elected in 1970, was President of the Royal Academy (1976-1984). A close friend of the British royal family, he designed the interior of the royal yacht Britannia and was also credited with teaching Charles, Prince of Wales to paint in watercolours.