American labour leader who served as president of the American Federation of Musicians (AFM) from 1940 to 1958.

Petrillo grew up on Chicago's west side and, after a brief period as a trumpet player and bandleader, became active in an independent musicians' union and served as its president for three years. Defeated for reelection, he joined the local chapter of the AFM in Chicago in 1918. In 1922 he became president of the Chicago local. Active in Democratic political circles, Petrillo used a position on Chicago's park board to initiate free summer concerts in Grant Park—a practice that has continued since 1936.

In 1940 Petrillo was elected national president of the AFM. Two years later, after U.S. entry into World War II, he called a general strike against the nation's record companies for their failure to pay royalties to musicians for sales on their recordings. Despite President Franklin D. Roosevelt's protestations that music was essential to national wartime morale, the union held out for 27 months before winning the desired concessions. This victory led to the establishment of the Music Performance Trust Fund, which for many years paid for free benefit concerts across the United States, kept musicians employed, and contributed to charitable causes. Petrillo fought to protect his union's membership from changes wrought by technological change in the entertainment and recording industry.