Sergei Rachmaninoff (Russian: Сергей Васильевич Рахманинов, Sergej Vasil'evič Rahmaninov, April 1, 1873 (N.S.) or March 20, 1873 (O.S.) – March 28, 1943) was a Russian composer, pianist, and conductor.

He was one of the greatest pianists of his generation, having legendary technical facilities and rhythmic drive. His large hands were able to cover the interval of a thirteenth on the keyboard (a hand span of approximately twelve inches). Many recordings were made by the Victor Talking Machine Company recording label of his performing his own music as well as works from the standard repertoire. He is often named as one of the greatest pianists of the twentieth century.

His reputation as a composer, on the other hand, has varied considerably since his death. The 1954 edition of Grove's Dictionary of Music and Musicians notoriously dismissed his music as "monotonous in texture ... consisting mainly of artificial and gushing tunes ..." and predicted that his popular success was "not likely to last". However ,his popularity among both musicians and audiences has, if anything, increased during the second half of the twentieth century, with some of his symphonies and other orchestral works, songs, and choral music recognized as masterpieces alongside the more familiar piano works.

His compositions include, among others, four piano concerti, three symphonies, two piano sonatas, three operas, a choral symphony (The Bells, based on the poem by Edgar Allan Poe), the All-Night Vigil for unaccompanied choir (often known as Rachmaninoff's Vespers), the Rhapsody on a Theme of Paganini, 24 Preludes (including the famous Prelude in C-sharp minor), 17 Études-tableaux, Symphonic Dances and many songs, of which the most famous is the wordless Vocalise. Most of his pieces are in a late Romantic style akin to Tchaikovsky, although strong influences of Chopin and Liszt are apparent. Further inspiration included the music of Balakirev, Mussorgsky, Medtner (whom he considered the greatest contemporary composer), and Henselt.