Sergei Vasilievich Rachmaninoff (Russian: Сергей Васильевич Рахманинов, Sergej Vasil'evič Rahmaninov, April 1, 1873 – March 28, 1943) was a Russian-born composer who later in life became an American citizen.

As a performer, composer, and conductor, Rachmaninoff is remembered as one of the true artistic geniuses of the late nineteenth and early twentieth century era. While his reputation as a composer only came later in life, Rachmaninoff's skill as pianist was well-known and highly respected throughout his life; he often performed his own works as soloist.

He was one of the greatest pianists of his generation, having legendary technical facilities and rhythmic drive, and his large hands were able to easily cover an interval of twelfth on the piano. His piano concertos are among the most demanding ever composed, as he sought to challenge both himself and other pianists to greater heights. Many recordings were made by the Victor Talking Machine Company recording label of him performing his own music as well as works from the standard repertoire.

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), a setting of the Vespers, Rhapsody on a Theme of Paganini, 41 Preludes and Etudes, Symphonic Dances and many songs. 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 Mily Balakirev, Mussorgsky, Nikolai Karlovich Medtner (whom he considered the greatest contemporary composer) and Adolf von Henselt.

Due to these influential composers, many of Rachmaninoff's symphonic works are in the modern idiom that corresponds with his twentieth century contemporaries. His life as both a performer and as a composer who raised to new heights the skills of others reveals the ideal of instruction by example. This way is best for elevating others, including as the way to raise up people in their spiritual and social responsibilities.