Orchestral jazz is a jazz genre developed in the United States in the 1920s, most significantly by Fletcher Henderson and Duke Ellington.
As early as the 1910s there had been dance orchestras playing the popular songs of the day along with a smattering of jazz. But the first to truly perform and record orchestral jazz was Fletcher Henderson, starting in about 1923, who gathered from smaller quintets and sextets a number of notable New York based players and formed the first full jazz orchestra. Henderson relied heavily on the arranging talent of the alto saxophonist and multi-instrumentalist Don Redman.
Among the most significant composers of Orchestral jazz was Duke Ellington, developing his mode at Harlem's Cotton Club in the late 1920s and early 1930s.