Charles Ives's Symphony No. 4, S. 4 was written between 1910 and the mid-1920s. The symphony is notable for its multilayered complexity—typically requiring two conductors in performance—and for its large and varied orchestration. Combining elements and techniques of Ives's previous compositional work, this has been called "one of his most definitive works"; Ives' biographer, Jan Swafford, has called it "Ives's climactic masterpiece".

Charles Edward Ives was an American actuary, businessman, and modernist composer. Ives was amongst the earliest American internationally renowned composers to achieve recognition on a global scale. His music was largely ignored during his early career, and many of his works went unperformed for many years. Later in life, the quality of his music was publicly recognized through the efforts of contemporaries like Henry Cowell and Lou Harrison, and he came to be regarded as an "American original". He was also among the first composers to engage in a systematic program of experimental music, with musical techniques including polytonality, polyrhythm, tone clusters, aleatory elements, and quarter tones. His experimentation foreshadowed many musical innovations that were later more widely adopted during the 20th century. Hence, he is often regarded as the leading American composer of art music of the 20th century.