Rex William Stewart Jr. (February 22, 1907 – September 7, 1967) was an American jazz cornetist who was a member of the Duke Ellingtonorchestra.

As a boy he studied piano and violin; most of his career was spent on cornet. Stewart dropped out of high school to become a member of the Ragtime Clowns led by Ollie Blackwell. He was with the Musical Spillers led by Willie Lewis in the early 1920s, then with Elmer Snowden, Horace Henderson, Fletcher Henderson, Fess Williams, and McKinney’s Cotton Pickers. In 1933 he led a big band at the Empire Ballroom in New York City. Beginning in 1934, he spent eleven years with the Duke Ellington band. Stewart co-wrote “Boy Meets Horn” and “Morning Glory” and supervised recording sessions by members of the Ellington band. He left Ellington to lead “little swing bands that were a perfect setting for his solo playing.” He toured in Europe and Australia with Jazz at the Philharmonic from 1947 to 1951.