Leon Bismark "Bix" Beiderbecke (March 10, 1903 – August 6, 1931) was an American jazz cornetist, jazz pianist, and composer.

With Louis Armstrong, Beiderbecke was one of the most influential jazz soloists of the 1920s. His turns on "Singin' the Blues" (1927) and "I'm Coming, Virginia" (1927), in particular, demonstrated an unusual purity of tone and a gift for improvisation. With these two recordings, especially, he helped to invent the jazz ballad style and hinted at what, in the 1950s, would become cool jazz. "In a Mist" (1927), one of a handful of his piano compositions but the only one he recorded, mixed classical influences with jazz syncopation. Beiderbecke also has been credited for his influence, directly, on Bing Crosby and, indirectly, via saxophonist Frank Trumbauer, on Lester Young.