Swing music, or simply swing, is a form of American music that developed in the early 1930s and became a distinctive style by 1935. 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.The name swing came from the phrase ‘swing feel’ where the emphasis is on the off–beat or weaker pulse in the music ( unlike classic music). Swing bands usually featured soloists who would improvise on the melody over the arrangement. The danceable swing style of big bands and bandleaders such as Benny Goodman and Count Basie was the dominant form of American popular music from 1935 to 1945, a period known as the Swing Era.

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.