Marshall Belford Allen (born May 25, 1924)  is an American free jazz and avant-garde jazz alto saxophone player. He also performs on flute, oboe, piccolo, and EWI (an electronic valve instrument made by Steiner, Crumar company).

Allen is best known for his work with Sun Ra, having recorded and performed mostly in this context since the late 1950s, and having led Sun Ra’s Arkestra since 1993, after Sun Ra’s Death. Critic Jason Ankeny describes Marshall as “one of the most distinctive and original saxophonists of the postwar era.” Marshall Allen was born in Louisville, Kentucky, United States.

During the Second World War he enlisted in the 92nd Infantry Division and was stationed in France. Allen studied alto saxophone in Paris and played in Europe with Art Simmons and James Moody.

He is best known for his mastery of pyrotechnic effects on the alto – he has said that he “wanted to play on a broader sound basis rather than on chords” (1971 interview with Tam Fiofori)). The opportunity came through his long association with Sun Ra, with whom he performed almost exclusively from 1958 to Ra’s death in 1993, although he did record outside the Arkestra, with Paul Bley‘s group in 1964 and Olatunji‘s group during the mid-1960s. Critic Scott Yanow has described Allen’s playing as “Johnny Hodges from another dimension”.