The Federal Bureau of Investigation (FBI) is the domestic intelligence and security service of the United States and its principal federal law enforcement agency. Operating under the jurisdiction of the United States Department of Justice, the FBI is also a member of the U.S. Intelligence Community and reports to both the Attorney General and the Director of National Intelligence. A leading U.S. counter-terrorism, counterintelligence, and criminal investigative organization, the FBI has jurisdiction over violations of more than 200 categories of federal crimes.

Although many of the FBI's functions are unique, its activities in support of national security are comparable to those of the British MI5 and the Russian FSB. Unlike the Central Intelligence Agency (CIA), which has no law enforcement authority and is focused on intelligence collection abroad, the FBI is primarily a domestic agency, maintaining 56 field offices in major cities throughout the United States, and more than 400 resident agencies in smaller cities and areas across the nation. At an FBI field office, a senior-level FBI officer concurrently serves as the representative of the Director of National Intelligence.

Despite its domestic focus, the FBI also maintains a significant international footprint, operating 60 Legal Attache (LEGAT) offices and 15 sub-offices in U.S. embassies and consulates across the globe. These foreign offices exist primarily for the purpose of coordination with foreign security services and do not usually conduct unilateral operations in the host countries. The FBI can and does at times carry out secret activities overseas, just as the CIA has a limited domestic function; these activities generally require coordination across government agencies.

The FBI was established in 1908 as the Bureau of Investigation, the BOI or BI for short. Its name was changed to the Federal Bureau of Investigation (FBI) in 1935. The FBI headquarters is the J. Edgar Hoover Building, located in Washington, D.C.

Budget, mission, and priorities

FBI Domestic Investigations and Operations Guide
In the fiscal year 2019, the Bureau's total budget was approximately $9.6 billion.

The FBI's main goal is to protect and defend the United States, to uphold and enforce the criminal laws of the United States, and to provide leadership and criminal justice services to federal, state, municipal, and international agencies and partners.

Currently, the FBI's top priorities are:

Protect the United States from terrorist attacks
Protect the United States against foreign intelligence operations and espionage
Protect the United States against cyber-based attacks and high-technology crimes
Combat public corruption at all levels
Protect civil rights
Combat transnational/national criminal organizations and enterprises
Combat major white-collar crime
Combat significant violent crime
Support federal, state, local and international partners
Upgrade technology to enable, and further, the successful performances of its missions as stated above

I have no affiliations with the CIA