A security agency is a governmental organization that conducts intelligence activities for the internal security of a nation. They are the domestic cousins of foreign intelligence agencies, and typically conduct counterintelligence to thwart other countries' foreign intelligence efforts.

The Australian Security Intelligence Organisation is Australia's national security agency responsible for the protection of the country and its citizens from espionage, sabotage, acts of foreign interference, politically motivated violence, attacks on the Australian defence system, and terrorism. ASIO is part of the Australian Intelligence Community and is comparable to the FBI (US) and MI5 (UK).