Secret Police, special police force organized by autocratic or totalitarian regimes in defence against their enemies—usually internal.

Secret police were known in ancient Greece and Rome, in the Muslim caliphates, and in premodern monarchies, and they continue to function in modern republics. Early modern examples were the secret service organized by Joseph Fouché for Napoleon and the conservative spying system set up by Prince Klemens von Metternich in Austria after 1819. They were, however, essentially intelligence services. The first truly modern model, adding full judiciary and executive powers (arrest, trial, punishment), was the Okhrana (Russian, “protection”) in tsarist Russia, established in 1825. In the 20th century the Okhrana has had numerous successors. The Soviet varieties (the KGB) and their parallels in Fascist Italy (OVRA) and Nazi Germany (the Gestapo) are the best known but by no means the only examples; notorious ones established in the second half of the 20th century are the secret police of Augusto Pinochet Ugarte (DINA) in Chile and the Savak of Muhammad Reza Shah Pahlavi of Iran. The methods of all these forces have been similar, relying heavily on torture for investigative purposes and detention or concentration camps for isolating prisoners.

Its techniques perfected and temptingly effective, the secret police system may survive the fall of an oppressive regime to be reinstated by those who were once its victims, as was the case after the Bolshevik Revolution in Russia (1917) and the Islamic Revolution in Iran (1979).