John Edgar Hoover (January 1, 1895 – May 2, 1972) was an American law-enforcement administrator who served as the first Director of the Federal Bureau of Investigation (FBI). Calvin Coolidge appointed Hoover as director of the Bureau of Investigation—the FBI's predecessor—in 1924, and in 1935 Hoover became instrumental in founding the FBI, where he remained director for 37 years until his death in 1972. Hoover expanded the FBI into a larger crime-fighting agency and instituted a number of modernizations to policing technology, such as a centralized fingerprint file and forensic laboratories. Hoover also established and expanded a national blacklist, referred to as the FBI Index or Index List.

Later in life and after his death, Hoover became a controversial figure as evidence of his secretive abuses of power began to surface. He was found to have routinely violated both the FBI's own policies and the very laws which the FBI was charged with enforcing, to have used the FBI to harass and sabotage political dissidents, to amass secret files for blackmailing high-level politicians, and to have collected evidence using illegal surveillance, wiretapping, and burglaries. Hoover consequently amassed a great deal of power and was able to intimidate and threaten political figures.