Walton was born in Oldham, Lancashire in 1902 to a very musical family; his father, Charles Walton, was a choirmaster and singing teacher, whilst his mother, Louisa (née Turner), was a singer. Walton himself was a chorister at Christ Church Cathedral at Oxford from the age of ten, and at the tender age of 16 went on to study at the university, the Dean of Christ Church having taken a strong interest in him. However, he left Oxford without a degree, and from 1920 lived with the Sitwell family in London, whom he had met during his studies at Oxford.
The three Sitwells siblings, all budding poets, introduced him to many major musical and literary figures of the time, including Delius , Diaghilev, and T. S. Eliot. The period also afforded him the opportunity to compose. His 'entertainment' Façade (1921) soon became popular as an orchestral suite and ballet. Walton spent the following years immersed in jazz, although little work from this period now remains, excepting the clear influence of jazz upon his next important work: the overture Portsmouth Point (1925). The introspective Viola Concerto (1928-29), seemingly modelled on Prokofiev's Violin Concerto No. 1, solidified his reputation in England. A commission by the BBC resulted in the landmark choral work, Belshazzar's Feast (1931), which attracted a strong response from the critics for its 'pagan overtones' and musical modernity. This and the First Symphony (1935) composed for conductor Hamilton Harty extended his reputation internationally, the latter inspired by his stormy love affair with Baroness Imma Doernberg. It was during this period that he began to detach himself from the Sitwell family, and began to attract such patrons as Siegfried Sassoon, Mrs Samuel Courtauld and Lady Alice Wimbourne.
Walton only really began to get an income from his compositions, however, after he began to compose music for films, through the influence of the director Paul Czinner. His extensive involvement with the film world reached its climax with his collaboration with Laurence Olivier on three Shakespeare films; Henry V (1943-4), Hamlet (1947) and Richard III (1955). Walton spent much of World War II concentrating on composing scores for patriotic films, after which he turned to chamber music and the eight-year project Troilus and Cressida (1947-54), a tragic opera after the style of Puccini. Performed in Covent Garden in 1954, and later in New York and San Francisco, and at La Scala, this latter work attracted much criticism, as 'hopelessly out of date, both musically and psychologically.' Walton was deeply affected by such criticism of a work so close to his heart, and went on to revise the work well into the 1970s. Walton had also lost his place in the eyes of the critics as foremost composer of Britain to the rising star of Benjamin Britten . Walton's musical output, already low, began to slow.
Nevertheless, Walton continued to work to commission, including an excellent Cello Concerto (1957) for Gregor Piatigorsky, a Partita for Orchestra (1958) for the conductor Georg Szell, Variations on a Theme of Hindemith (1963) for the Royal Philharmonic Society , and the opera The Bear (1967) commissioned for the Aldeburgh Festival and described as an 'extravaganza in one act.'
Despite his increasingly ill health Walton undertook tours in his later years, conducting and attending performances of his own works, notably in Australia and New Zealand in 1964 and Russia in 1971, where he received a tumultuous welcome.
During his long career Walton received many awards: 7 honorary doctorates, the Gold Medal of the Royal Philharmonic Society (1947); a knighthood (1951); the Order of Merit (1967); and the Benjamin Franklin Medal (1972). He was elected to honorary membership in the American Academy of Arts and Letters (1978) and received the Ivor Novello Award (1982).
In the later years of his life, Walton lived on the island of Ischia, near Naples. He remained an active composer until his death there in 1983.