Weldon Leo "Jack" Teagarden (August 20, 1905–January 15, 1964), known as "Big T", was an influential jazz trombonist, bandleader, composer, and vocalist.

Born in Vernon, Texas, his brothers Charlie and Clois "Cub" and his sister Norma also became noted professional musicians. Teagarden's father was an amateur brass band trumpeter and started young Jack on baritone horn; by age 10 he had switched to trombone. He first heard jazz music played by the Louisiana Five and decided to play in the new style.

Teagarden's trombone style was largely self-taught, and he developed many unusual alternative positions and novel special effects on the instrument. He is usually considered the most innovative white jazz trombone stylist of the pre-Bebop era, and did much to expand the role of the instrument beyond the old tailgate style role of the early New Orleans brass bands. Chief among his contributions to the language of jazz trombonists was his ability to interject the blues or merely a "blue feeling" into virtually any piece of music.