The Reign of Terror (5 September 1793 27 July 1794), also known as the The Terror (French: la Terreur) was a period of violence that occurred fifty months after the onset of the French Revolution, incited by conflict between rival political factions, the Girondins and the Jacobins, and marked by mass executions of "enemies of the revolution." Estimates vary widely as to how many were killed, with numbers ranging from 20,000 to 40,000; in many cases, records were not kept, or if they were, they are considered likely to be inaccurate. The guillotine ("National Razor") became the symbol of a string of executions: Marie-Antoinette, the Girondins Philippe Égalité and Madame Roland, as well as many others, such as "the father of modern chemistry" Antoine Lavoisier, lost their lives under its blade.
During 1794, the revolutionary government of France was threatened by internal enemies, conspirators, and foreign monarchies. Within France the revolution was opposed by the former French nobility, which had lost its inherited privileges. The Roman Catholic Church was generally against the Revolution, which had turned the clergy into employees of the state and required they take an oath of loyalty to the nation (through the Civil Constitution of the Clergy). In addition, the First French Republic was engaged in a series of French Revolutionary Wars with neighboring powers. European monarchies wanted to stifle the democratic and republican ideals that might threaten their own stability.
The extension of civil war and the advance of foreign armies on national territory produced a political crisis, and increased the rivalry between the Girondins and the more radical Jacobins; the latter were eventually grouped in the parliamentary faction called the Mountain, and had the support of the Parisian population. The French government established the Committee of Public Safety, which took its final form on 6 September 1793 and was ultimately dominated by Maximilien Robespierre, in order to suppress internal counter-revolutionary activities and raise additional French military force. Through the Revolutionary Tribunal, the Terror's leaders exercised broad dictatorial powers and used them to instigate mass executions and political purges. The repression accelerated in June and July 1794, a period called "la Grande Terreur" (The Great Terror), and ended in the "Thermidorian Reaction," or coup of 9 Thermidor Year II (27 July 1794), in which several leaders of the Reign of Terror were executed, including Louis de Saint-Just and Robespierre.