Revolutionary terror (also referred to as Revolutionary terrorism, or a reign of terror)) refers to the institutionalized application of force to counterrevolutionaries, 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 the Russian Soviet Federative Socialist Republic (RSFSR) to the reign of the Khmer Rouge, and others.
In contrast the reactionary terror, such as , has been used to subdue revolutions.
In his article, The Victory of the Counter-Revolution in Vienna, Neue Rheinische Zeitung, No. 136, 7 November 1848, Karl Marx wrote: “… there is only one means to shorten, simplify and concentrate the murderous death throes of the old society and the bloody birth pangs of the new, only one means – revolutionary terrorism (the term terrorism, here, not to be confused with the modern meaning of the term, but rather having the same meaning as the word terror in the sense in which it is used in this article).
Edvard Radzinsky, a Russian author of popular history books, in his biography of Joseph Stalin noted that Stalin wrote a nota bene — "Terror is the quickest way to new society" — beside the above passage in a book by Karl Kautsky.
Lenin, Leon Trotsky and other leading Bolshevik ideologists recognized mass terror as a necessary weapon during the dictatorship of proletariat and the resulting class struggle. Thus, in his The Proletarian Revolution and the Renegade K. Kautsky (1918), Lenin wrote: “One cannot hide the fact that dictatorship presupposes and implies a “condition”, one so disagreeable to renegades [such as Kautsky], of revolutionary violence of one class against another … the “fundamental feature” of the concept of dictatorship of the proletariat is revolutionary violence.”