Swing music, also known as swing jazz or simply swing, is a form of jazz music that developed in the early 1930s and became a distinctive style by 1935 in the United States. Swing uses a strong rhythm section of double bass and drums as the anchor for a lead section of brass instruments such as trumpets and trombones, woodwinds including saxophones and clarinets, and sometimes stringed instruments such as violin and guitar, medium to fast tempos, and a "lilting" swing time rhythm. Swing bands usually featured soloists who would improvise on the melody over the arrangement. The danceable swing style of bandleaders such as Benny Goodman and Count Basie was the dominant form of American popular music from 1935 to 1945. The verb "to swing" is also used as a term of praise for playing that has a strong rhythmic "groove" or drive.

The styles of jazz that were popular from the late teens through the late 1920s were usually played with rhythms with a two beat feel, and often attempted to reproduce the style of contrapuntal improvisation developed by the first generation of jazz musicians in New Orleans. In the late 1920s, however, larger ensembles using written arrangements became the norm, and a subtle stylistic shift took place in the rhythm, which developed a four beat feel with a smoothly syncopated style of playing the melody, while the rhythm section supported it with a steady four to the bar. Like jazz, swing was created by African Americans, and its impact on the overall American culture was such that it marked and named an entire era of the USA, the swing era - as the 1920s had been termed "The Jazz Age".[1] Such an influence from the Black community was unprecedented in any western country.[1] Swing music abandoned the string orchestra and used simpler, "edgier" arrangements that emphasized horns and wind instruments and improvised melodies.

Louis Armstrong, who would later publicly ridicule bebop, shared a different version of the history of swing during a nationwide broadcast of the Bing Crosby (radio) Show Crosby said, "We have as our guest the master of swing and I'm going to get him to tell you what swing music is." He asked Louis to explain it. Louis said, "Ah, swing, well, we used to call it ragtime, then bluesthen jazz. Now, it's swing. White folks yo'all sho is a mess. Swing!"