Piano Concerto No. 4 in G minor, Op. 40, is a major work by Russian composer Sergei Rachmaninoff, completed in 1926. The work exists in three versions. Following its unsuccessful premiere, the composer made cuts and other amendments before publishing it in 1928. With continued lack of success, he withdrew the work, eventually revising and republishing it in 1941. The original manuscript version was released in 2000 by the Rachmaninoff Estate to be published and recorded. The work is dedicated to Nikolai Medtner, who in turn dedicated his Second Piano Concerto to Rachmaninoff the following year.

Sergei Vasilyevich Rachmaninoff was a Russian composer, virtuoso pianist, and conductor. Rachmaninoff is widely considered one of the finest pianists of his day and, as a composer, one of the last great representatives of Romanticism in Russian classical music. Early influences of Tchaikovsky, Rimsky-Korsakov, and other Russian composers gave way to a thoroughly personal idiom notable for its song-like melodicism, expressiveness, dense contrapuntal textures, and rich orchestral colours. The piano is featured prominently in Rachmaninoff's compositional output and he used his skills as a performer to fully explore the expressive and technical possibilities of the instrument.