The Committee for State Security was the main security agency for the Soviet Union from 13 March 1954 until 3 December 1991. As a direct successor of preceding agencies such as the Cheka, GPU, OGPU, NKGB, NKVD and MGB, it was attached to the Council of Ministers. It was the chief government agency of "union-republican jurisdiction", carrying out internal security, foreign intelligence, counter-intelligence and secret police functions. Similar agencies operated in each of the republics of the Soviet Union aside from the Russian SFSR, where the KGB was headquartered, with many associated ministries, state committees and state commissions.

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.