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 the electronic EWI.

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 The Sun Ra Arkestra since 1995, after Sun Ra’s death in 1993 and John Gilmore‘s death two years later. Critic Jason Ankeny describes Marshall as “one of the most distinctive and original saxophonists of the postwar era.”

Marshall Belford 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.