The Great Purge was a series of campaigns of political repression and murder in the Soviet Union orchestrated by Joseph Stalin from 1937 to 1938. It involved a large-scale purge of the Communist Party and government officials, repression of peasants, Red Army leadership, and the persecution of unaffiliated persons, characterized by widespread police surveillance, widespread suspicion of "saboteurs", imprisonment, and arbitrary executions. In Russian historiography the period of the most intense purge, 1937–1938, is called Yezhovshchina (Russian: ежовщина; literally, the Yezhov regime), after Nikolai Yezhov, the head of the Soviet secret police, NKVD.

In the Western world, Robert Conquest's 1968 book The Great Terror popularized that phrase. Conquest's title was in turn inspired by the period of terror (French: la Terreur) during the French Revolution.

The term "repression" was officially used to denote the prosecution of people considered as counter-revolutionaries and enemies of the people. The purge was motivated by the desire on the part of the leadership to remove dissenters from the Party and what is often considered to have been a desire to consolidate the authority of Joseph Stalin. Additional campaigns of repression were carried out against national minorities and social groups which were accused of acting against the Soviet state and the politics of the Communist Party.

The term show trial is a pejorative description of a type of highly public trial in which there is a strong connotation that the judicial authorities have already determined the guilt of the defendant. The actual trial has as its only goal to present the accusation and the verdict to the public as an impressive example and as a warning. Show trials tend to be retributive rather than correctional justice. The term was first recorded in the 1930s.

Cadaver Trial was a posthumous trial over Catholic Pope Formosus held in 897.

In the late 17th century, various people in Salem, Massachusetts were accused of practicing witchcraft and consorting with the Devil in the Salem witch trials. Nineteen people were executed, one was killed, and five died in prison.

The Dreyfus affair was a show trial in France in 1894, where a Jewish captain, Alfred Dreyfus, was accused of spying for Germany.

The trial of Sacco and Vanzetti in 1927 was one in which two anarchist Italian immigrants were accused of an armed robbery in Massachusetts. Both were executed, despite international appeals.

Joseph Vissarionovich Stalin (Russian: Иосиф Виссарионович Сталин; born Iosif Vissarionovich Dzhugashvili, Russian: Иосиф Виссарионович Джугашвили; 18 December 1878 – 5 March 1953) was the Premier of the Soviet Union from 6 May 1941 to 5 March 1953. He was among the Bolshevik revolutionaries who brought about the October Revolution in Russia in 1917 and later held the position of General Secretary of the Communist Party of the Soviet Union's Central Committee from 1922 until his death in 1953. While the office of the General Secretary was officially elective and not initially regarded as the top position in the Soviet state, Stalin managed to use it to consolidate more and more power in his hands after the death of Vladimir Lenin in 1924 and gradually put down all opposition groups within the Communist Party. This included Leon Trotsky, a socialist theorist and the principal critic of Stalin among the early Soviet leaders, who was exiled from the Soviet Union in 1929. Whereas Trotsky was an exponent of permanent revolution, it was Stalin's concept of socialism in one country that became the primary focus of Soviet politics.