Sir Adrian Cedric Boult, CH (/boʊlt/; 8 April 1889 – 22 February 1983) was an English conductor. Brought up in a prosperous mercantile family, he followed musical studies in England and at Leipzig, Germany, with early conducting work in London for the Royal Opera House and Sergei Diaghilev's ballet company. His first prominent post was conductor of the City of Birmingham Orchestra in 1924. When the British Broadcasting Corporation appointed him director of music in 1930, he established the BBC Symphony Orchestra and became its chief conductor. The orchestra set standards of excellence that were rivalled in Britain only by the London Philharmonic Orchestra (LPO), founded two years later.

Forced to leave the BBC in 1950 on reaching retirement age, Boult took on the chief conductorship of the LPO. The orchestra had declined from its peak of the 1930s, but under his guidance its fortunes were revived. He retired as its chief conductor in 1957, and later accepted the post of president. Although in the latter part of his career he worked with other orchestras, including the London Symphony Orchestra, the Philharmonia Orchestra, the Royal Philharmonic Orchestra, and his former orchestra, the BBC Symphony, it was the LPO with which he was primarily associated, conducting it in concerts and recordings until 1978, in what was widely called his "Indian Summer".