John Casimir (16 October 1898 – 3 January 1963) was a New Orleans jazz clarinetist and bandleader, best remembered as the leader ofThe Young Tuxedo Brass Band for some 20 years up to his death.
Casimir started playing professionally with the Young Eagles Band with Lee Collins in 1919.
He was also a member of the Original Tuxedo Brass Band, often following the lead of Louis Armstrong.
The Young Tuxedo Brass Band's 1958 album was released under the title"Jazz Begins" by Atlantic Records. It was the only recording the band released under his leadership. Casimir also led a dance band using some of the same musicians under the name The Young Tuxedo Jazz Band, which also recorded. Casimir played Bb clarinet with the jazz band, and the distinctive higher Eb clarinet with brass bands.