The Federal Bureau of Investigation (FBI) is a federal criminal investigative, intelligence agency, and the primary investigative arm of the United States Department of Justice (DOJ). At present, the FBI has investigative jurisdiction over violations of more than 200 categories of federal crimes and thus has the broadest investigative authority of any U.S. federal law enforcement agency. The motto of the bureau is "Fidelity, Bravery, Integrity."

Starting in 1908 as the Bureau of Investigation (BOI) it did not rename to the Federal Bureau of Investigation until 1935. J. Edgar Hoover, the first FBI Director, continuing his tenure from the BOI, was the longest serving FBI director to date. He also is responsible for many of the advancements and changes he made as the FBI director for it to become a leading agency in the world. The J. Edgar Hoover building, FBI Academy, and the Criminal Justice Information Services Complex serve as the main support offices for each of the field offices that are located throughout the country.

As one of the primary investigative and intelligence agencies of the United States, its collection and publications of crime statistics keeps the public aware of crime rates and the types of crime that has been committed. Before the September 11, 2001 attacks, the FBI only had a marginal role in trying to prevent crime before it happens. Now the FBI actively attacks potential threats before they can take place.