The Modern Jazz Quartet (MJQ) was a prominent American jazz ensemble formed in 1952, known for its sophisticated blend of classical music influences, cool jazz, blues, and bebop. The group originally consisted of Milt Jackson on vibraphone, John Lewis on piano, Percy Heath on double bass, and Kenny Clarke on drums. Clarke was later replaced by Connie Kay in 1955. The MJQ emerged from the rhythm section of Dizzy Gillespie's big band, with Lewis becoming the musical director. They were noted for their elegant and restrained style, often performing in concert halls rather than nightclubs, which was unusual for jazz ensembles of the time.

The MJQ's repertoire included original compositions by Lewis and Jackson, such as "Django" and "Bags' Groove," as well as classical and jazz standards. Their music often featured intricate counterpoint and baroque influences, particularly in Lewis's compositions like "Concorde" and "Fontessa." The group was also involved in film scoring, with works such as "No Sun in Venice" and "Odds Against Tomorrow."

The MJQ was active until 1974 when they disbanded due to financial and touring frustrations but reunited in 1981 for annual tours. They continued to perform until 1997, with Albert Heath replacing Kay after his death in 1994. The MJQ's legacy is marked by their high performance standards and their role in pioneering chamber jazz, blending jazz improvisation with classical music elements.