Milt Jackson, byname of Milton Jackson, also nicknamed "Bags", (born January 1, 1923, Detroit, Michigan, U.S.—died October 9, 1999, New York, New York), American jazz musician, the first and most influential vibraphone improviser of the postwar, modern jazz era. Jackson began playing the vibraphone (also called vibes or vibraharp) professionally at age 16.

He attended Michigan State University and joined Dizzy Gillespie’s sextet in 1945; he then worked with Gillespie’s big band and later returned to play vibraphone and piano in Gillespie’s sextet (1950–52). He also freelanced with leading bop musicians in New York City and played in the Woody Herman band (1949–50). He was a cofounder of the Modern Jazz Quartet (MJQ), which was his principal performance vehicle during 1952–74, and he subsequently played in numerous MJQ reunion tours. Meanwhile, he recorded often as sideman, including classic sessions with Thelonious Monk (“Evidence,” “Criss Cross,” “Straight, No Chaser”) and Miles Davis (“Bags’ Groove”), and as leader, including performances with top tenor saxophonists Coleman Hawkins, John Coltrane, and Lucky Thompson.

He continued to tour and record in the 1990s; one of his last recordings was with jazz legends Oscar Peterson and Ray Brown, with whom Jackson had formed the Very Tall Band years earlier. A fluent player with compelling swing who conceived in long lines of eighth and sixteenth notes, Jackson created an original style out of bebop’s advanced harmonies and irregular accenting. By manipulating his vibrato speed he achieved a unique depth and beauty of expression on the vibraphone, a traditionally “cold” instrument, adding special warmth to his playing of ballads and medium-tempo blues. Jackson brought to his musical settings a highly developed sensitivity to balance and contrast, which made much of his playing with the MJQ muted when compared with his aggressive work in his own groups.