Sergei Vasilievich Rachmaninoff (Russian: Сергей Васильевич Рахманинов, Sergej Vasil’evič Rakhmaninov, 1 April 1873 – 28 March 1943) was a Russian composer, pianist, and conductor. He was one of the finest pianists of his day and, as a composer, the last great representative of Russian late Romanticism in classical music. Early influences of Tchaikovsky, Rimsky-Korsakov and other Russian composers gave way to a thoroughly personal idiom which included a pronounced lyricism, expressive breadth, structural ingenuity and a tonal palette of rich, distinctive orchestral colors.

The piano figures prominently in Rachmaninoff's compositional output, either as a solo instrument or as part of an ensemble. He made it a point, however, to use his own skills as a performer to explore fully the expressive possibilities of the instrument. Even in his earliest works, he revealed a sure grasp of idiomatic piano writing and a striking gift for melody.

Rachmaninoff was born in 1873 in Semyonovo, near Novgorod, in north-western Russia. His parents were both amateur pianists. When he was four, his mother gave him casual piano lessons, but it was his paternal grandfather, Arkady Alexandrovich Rachmaninoff, who brought Anna Ornatskaya, a teacher from Saint Petersburg, to teach Sergei in 1882. Ornatskaya remained for "two or three years", until the family home had to be sold to settle debts and the Rachmaninoffs moved to Moscow.