The FBI is the lead agency in the fight against terrorism in the United States. Terrorism can originate both from outside the country, as with the World Trade Center Bombing in New York City, and fromwithin the US, as demonstrated by the Oklahoma City Bombing. The FBI maintains close working relationships with other government intelligence agencies, as well as with foreign agencies, that provide beneficial resources in preventing and responding to potential terroristic threats to the United States. To further assist in this area of law enforcement, the FBI has established the Counterterrorism Center, in conjunction with 18 federal agencies, to provide immediate real-time assistance in the event of an act of terror within the US.

Within the United States, the FBI is also the lead agency in responding to acts of Nuclear, Biological, or Chemical terrorism. In all of these potential cases, the Bureau plays a key role in the planning and logistics of Special Events.