Revolutionary terror, also referred to as revolutionary terrorism or reign of terror, refers to the institutionalized application of force to counter-revolutionaries, particularly during the French Revolution from the years 1793 to 1795. The term "Communist terrorism" has also been used to describe the revolutionary terror, from the Red Terror in Russia and Cultural Revolution in China to the reign of the Khmer Rouge and others. In contrast, "reactionary terror", often called White Terrors, has been used to subdue revolutions.

The Reign of Terror was a period of the French Revolution when, following the creation of the First Republic, a series of massacres and numerous public executions took place in response to revolutionary fervour, anticlerical sentiment, and accusations of treason by the Committee of Public Safety. While terror was never formally instituted as a legal policy by the Convention, it was more often employed as a concept.