John Edgar Hoover (January 1, 1895 – May 2, 1972), generally known as J. Edgar Hoover, was the first Director of the Federal Bureau of Investigation (FBI) of the United States. Appointed director of the Bureau of Investigation—predecessor to the FBI—in 1924, he was instrumental in founding the FBI in 1935, where he remained director until his death in 1972. Hoover is credited with building the FBI into a large and efficient crime-fighting agency, and with instituting a number of modern innovations to police technology, such as a centralized fingerprint file and forensic laboratories.

Hoover was highly regarded by much of the U.S. public, but posthumously he became an increasingly controversial figure. His many critics asserted that he exceeded the jurisdiction of the FBI. He used the FBI to harass political dissenters and activists, to amass secret files on political leaders, and to use illegal methods to collect evidence. It is because of Hoover's long and controversial reign that FBI directors are now limited to 10-year terms.

Hoover was born on New Year's Day in 1895 in Washington, D.C., to Anna Marie Scheitlin, who was descended from a line of Swiss mercenaries, and Dickerson Naylor Hoover, Sr., of English and German stock, and grew up in the Eastern Market. Annie's uncle had been the Swiss honorary consul general to the U.S. Hoover worked at the Library of Congress during college and also became a member of Kappa Alpha Order (Alpha Nu 1914). In 1917 Hoover obtained a law degree from George Washington University. While a law student, Hoover became interested in the career of Anthony Comstock, the New York City U.S. Postal Inspector, who waged prolonged campaigns against fraud and vice (as well as pornography and information on birth control) a generation earlier. Hoover is thought to have studied Comstock's methods and modeled his early career on Comstock's reputation for relentless pursuit and occasional procedural violations in crime fighting.