Thomas Joseph Pendergast, also known as T. J. Pendergast, was an American political boss who controlled Kansas City and Jackson County, Missouri, from 1925 to 1939.
Pendergast only briefly held elected office, as an alderman, but his capacity as chairman of the Jackson County Democratic Party allowed him to use his large network of family and friends to help the election of politicians, in some cases by voter fraud, and to hand out government contracts and patronage jobs. He became wealthy in the process, but his addiction to gambling, especially horse racing, later led to a large accumulation of personal debts.
In 1939, he was convicted of income tax evasion and served 15 months in a federal prison. The Pendergast organization helped to launch the political career of future US President Harry S. Truman, which caused Truman's early enemies to dub him "the senator from Pendergast".