Jack Benny (born Benjamin Kubelsky) was a comedian, vaudeville performer, film actor, and one of the most prominent early stars of American radio and television. Often cited for his impeccable comic timing, Benny was an influential comedy innovator, a major architect of the modern forms of standup comedy and situation comedy.

Benny grew up in Chicago and Waukegan, Illinois. He began studying the violin, an instrument that would become his trademark, when he was six. By fourteen he was playing in local dance bands, as well as in his high school orchestra, until he failed school and left for a career in vaudeville. In 1911, he was playing in the same theater as the young Marx Brothers, whose mother was so enchanted with Benny that she invited him to be their permanent accompanist. The plan was foiled by Benny's parents, who refused to let their son, then seventeen, go on the road, but it was the beginning of his long friendship with Zeppo Marx.

The following year, Benny formed a vaudeville musical duo with pianist Cora Salisbury. This provoked famous violinist Jan Kubelik, who thought that the young vaudeville entertainer with a similar name (Kubelsky) would damage his reputation. Finally, Bejamin Kubelsky agreed to change his name to Ben K. Benny (sometimes spelled Bennie). He also found a new pianist, Lyman Wood. He left show business briefly in 1917 to join the Navy during World War I, but even then, he often entertained the troops. One evening, he was booed by the troops, so he began telling Navy jokes on stage. He was a big hit, earning himself a reputation as a comedian as well as a musician.

After the war, Benny returned to vaudeville and changed his first name to Jack. He had several romantic encounters, including with a dancer, Mary Kelly, whose devoutly Catholic family forced her to turn down Benny's proposal because he was Jewish. In 1922, he accompanied Zeppo Marx to a Passover seder in Vancouver, where he met Sadie Marks, whom he eventually married in 1927. As Mary Livingstone, she was his collaborator throughout much of his career.