Secret Police, police who operate secretly and are used for political purposes. They are also called secret political police. Secret police may wear uniforms or be a plain-clothes force. It is their task to control or suppress political opponents of the government. They often use intimidation to create a climate of fear, so that most people will conform.

Secret police are characteristic of police states, in which a totalitarian government or a dictator uses police to control almost every aspect of life. In these societies, secret police often act as judges, jailers, and executioners. When power struggles develop within these police states, the secret police are often used by one faction against the other. In democratic societies law and custom severely limit the power of police and of secret internal-security agents (such as those of the Federal Bureau of Investigation and U.S. Secret Service).

Secret police have been common wherever an oppressive minority government has sought to control a restless majority. The secret police of Sparta, in ancient Greece, were used to control the Helots (peasant serfs). Rulers of large empires such as the Roman Empire, the Inca Empire of South America, and the Mogul Empire of India often used secret police as political spies. Secret police were used as ruthless security agents by early European monarchs, Russian czars (especially Ivan IV and Nicholas I), and the leaders of the French Revolution. Napoleon I's secret police, created by Joseph Fouche, helped him control his European empire.

Notorious secret police of the 20th century have included Mussolini's secret police in Fascist Italy; the “Thought Police” of imperial Japan; and Nazi Germany's Gestapo, closely linked with the SS (Nazi party police) and SD (Security Service). Many Communist regimes and Third World dictatorships have also used secret police to prevent and suppress opposition.

The Soviet Union's secret police began with the Cheka, created by the Bolsheviks in 1917. The Cheka was reorganized under various names and agencies, including the OGPU, NKVD, NKGB, MGB, and MVD. In the 1930's, under Stalin, prisoners of the OGPU and NKVD were used as forced labor. After Stalin's death in 1953 the power of his police chief, Lavrenti P. Beria, momentarily rivaled that of the army and the Communist party itself. In 1954 the secret police were included in the KGB (Committee of State Security), an intelligence and internal security agency. In 1992, shortly after the collapse of the Soviet Union, the KGB was dissolved.