The State Protection Authority was the secret police of the People's Republic of Hungary from 1945 to 1956. The ÁVH was conceived as an external appendage of the Soviet Union's KGB in Hungary responsible for supporting the ruling Hungarian Working People's Party and persecuting political criminals. The ÁVH gained a reputation for brutality during a series of purges but was gradually reined in under the government of Imre Nagy, a moderate reformer, after he was appointed Prime Minister of Hungary in 1953. The ÁVH was dissolved by Nagy's revolutionary government during the Hungarian Revolution of 1956 and succeeded by the Ministry of Internal Affairs III.

Secret police are police, intelligence, or security agencies that engage in covert operations against a government's political, religious, or social opponents and dissidents. Secret police organizations are characteristic of authoritarian and totalitarian regimes. They protect the political power of a dictator or regime and often operate outside the law to repress dissidents and weaken political opposition, frequently using violence. They may enjoy legal sanction to hold and charge suspects without ever identifying their organization.