Olivier Messiaen (French: [ɔlivje mɛsjɑ̃]; December 10, 1908 – April 27, 1992) was a French composer, organist and ornithologist, one of the major composers of the 20th century. His music is rhythmically complex; harmonically and melodically it often uses modes of limited transposition, which he abstracted from his early compositions and improvisations. Messiaen also drew on his Roman Catholic faith for his pieces.

He travelled widely and wrote works inspired by diverse influences such as Japanese music, the landscape of Bryce Canyon in Utah and the life of St. Francis of Assisi. He said he perceived colours when he heard certain musical chords (a phenomenon known as synaesthesia in its literal manifestation); combinations of these colours, he said, were important in his compositional process. For a short period Messiaen experimented with the parametrisation associated with "total serialism", in which field he is often cited as an innovator. His style absorbed many exotic musical influences such as Indonesian gamelan (tuned percussion often features prominently in his orchestral works).