Dennis Brain, English composer (d. 1957)
Dennis Brain (17 May 1921 – 1 September 1957) was a British horn player. From a musical family – his father and grandfather were horn players – he attended the Royal Academy of Music in London. During the Second World War he served in the Royal Air Force, playing in its band and orchestra. After the war he was principal horn of the Philharmonia and Royal Philharmonic orchestras, and played in chamber ensembles.

Among the works written for Brain is Benjamin Britten's Serenade for Tenor, Horn and Strings (1944). Other composers who wrote for him include Malcolm Arnold, Lennox Berkeley, Alan Bush, Gordon Jacob, Humphrey Searle and Mátyás Seiber.

Brain was killed in a car crash at the age of 36.