The Reign of Terror (27 June 1793 – 27 July 1794), also known as the The Terror (French: la Terreur) was a period of violence that occurred for one year and two 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 16,000 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: Louis XVI, Marie Antoinette, the Girondins, Philippe Égalité (Louis Philippe II, Duke of Orléans) 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, revolutionary France was beset with real or imagined conspiracies by internal and foreign enemies. Within France the revolution was opposed by the 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.
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 coup of 9 Thermidor Year II (27 July 1794), the so-called "Thermidorian Reaction", in which several leaders of the Reign of Terror were executed, including Saint-Just and Robespierre.
On 7 September 1793, Paris sections — encouraged by the enragés ("enraged ones") Jacques Roux and Jacques Hébert — took over the Convention, calling for administrative and political purges, a low fixed price for bread, and a limitation of the electoral franchise to sans-culottes alone. With the backing of the National Guard, they persuaded the Convention to arrest 31 Girondist leaders, including Jacques Pierre Brissot. Following these arrests, the Jacobins gained control of the Committee of Public Safety on 10 June, installing the revolutionary dictatorship. On 13 July the assassination of Jean-Paul Marat — a Jacobin leader and journalist known for his bloodthirsty rhetoric — by Charlotte Corday, a Girondist, resulted in further increase of Jacobin political influence. Georges Danton, the leader of the August 1792 uprising against the King, was removed from the Committee. On 27 July Maximillien Robespierre, known in Republican circles as "the Incorruptible" for his ascetic dedication to his ideals, made his entrance, quickly becoming the most influential member of the Committee as it moved to take radical measures against the Revolution's domestic and foreign enemies.
Meanwhile, on 24 June the Convention adopted the first republican constitution of France, the French Constitution of 1793. It was ratified by public referendum, but never put into force; like other laws, it was indefinitely suspended by the decree of October that the government of France would be "revolutionary until the peace".
On 25 December 1793 Robespierre stated:
The goal of the constitutional government is to conserve the Republic; the aim of the revolutionary government is to found it... The revolutionary government owes to the good citizen all the protection of the nation; it owes nothing to the Enemies of the People but death... These notions would be enough to explain the origin and the nature of laws that we call revolutionary ... If the revolutionary government must be more active in its march and more free in his movements than an ordinary government, is it for that less fair and legitimate? No; it is supported by the most holy of all laws: the Salvation of the People.
On 5 February 1794 Robespierre stated, more succinctly that "Terror is nothing else than swift, severe, indomitable justice; it flows, then, from virtue." 
The result was policy through which the state used violent repression to crush resistance to the government. Under control of the effectively dictatorial Committee, the Convention quickly enacted more legislation. On 9 September the Convention established sans-culottes paramilitary forces, the revolutionary armies, to force farmers to surrender grain demanded by the government. On 17 September the Law of Suspects was passed, which authorized the charging of counter-revolutionaries with vaguely defined crimes against liberty. On 29 September the Convention extended price-fixing from grain and bread to other essential goods, and also fixed wages. The guillotine became the symbol of a string of executions: Louis XVI had already been guillotined before the start of the terror; Marie-Antoinette, the Girondists, Philippe Égalité, Madame Roland and many others lost their lives under its blade. The Revolutionary Tribunal summarily condemned thousands of people to death by the guillotine, while mobs beat other victims to death. Sometimes people died for their political opinions or actions, but many for little reason beyond mere suspicion, or because some others had a stake in getting rid of them.
Among people who were condemned by the revolutionary tribunals, about 8 percent were aristocrats, 6 percent clergy, 14 percent middle class, and 72 percent were workers or peasants accused of hoarding, evading the draft, desertion, rebellion, and other purported minimal crimes.
Another anti-clerical uprising was made possible by the installment of the Revolutionary Calendar on 24 October. Hébert's and Chaumette's atheist movement initiated a religious campaign in order to dechristianize society. The program of dechristianization waged against Catholicism, and eventually against all forms of Christianity, included the deportation of clergy and the condemnation of many of them to death, the closing of churches, the institution of revolutionary and civic cults, the large scale destruction of religious monuments, the outlawing of public and private worship and religious education, the forced abjurement of priests of their vows and forced marriages of the clergy,the word saint being removed from street names,and the War in the Vendée. The enactment of a law on 21 October 1793 made all suspected priests and all persons who harbored them liable to death on sight. The climax was reached with the celebration of the goddess "Reason" in Notre Dame Cathedral on 10 November. Because dissent was now regarded as counterrevolutionary, extremist enragés such as Hébert and moderate Montagnard indulgents such as Danton were guillotined in the Spring of 1794. On 7 June Robespierre, who favoured deism over Hébert's atheism and had previously condemned the Cult of Reason, advocated a new state religion and recommended that the Convention acknowledge the existence of God. On the next day, the worship of the deistic Supreme Being was inaugurated as an official aspect of the Revolution. Compared with Hébert's somewhat popular festivals, this austere new religion of Virtue was received with signs of hostility by the Parisian public.
The repression brought thousands of suspects before the Paris Revolutionary Tribunal, whose work was expedited by the Law of 22 Prairial (10 June 1794). As a result of Robespierre's insistence on associating Terror with Virtue, his efforts to make the republic a morally united patriotic community became equated with the endless bloodshed. Finally, after 26 June's decisive military victory over Austria at the Battle of Fleurus, Robespierre was overthrown by a conspiracy of certain members of the Convention on 9 Thermidor (27 July).
The fall of Robespierre was brought about by a combination of those who wanted more power for the Committee of Public Safety, and a more radical policy than he was willing to allow, with the moderates who opposed the Revolutionary Government altogether. They had, between them, made the Law of 22 Prairial one of the charges against him, and after his fall, advocating Terror would mean adopting the policy of a convicted enemy of the Republic, endangering the advocate's own head. Before his execution, Robespierre tried unsuccessfully to commit suicide by shooting himself, but the bullet merely shattered his jaw, and Robespierre was guillotined the next day.
The reign of the standing Committee of Public Safety was ended. New members were appointed the day after Robespierre's execution, and term limits were imposed (a quarter of the committee retired every three months); its powers were reduced piece by piece.
This was not an entirely or immediately conservative period; no government of the Republic envisaged a Restoration, and Marat was reburied in the Pantheon in September.
The Reign of Terror (5 September 1793 – 28 July 1794) or simply The Terror (French: la Terreur) was a period of about 11 months during the French Revolution. During this time, French people who did not support the revolution were executed at the guillotine.
The Reign of Terror started on 5 September, 1793. The violence happened more and more often in June and July of 1794, a period called la Grande Terreur (The Great Terror), which ended 27 July 1794, when several important leaders of the Reign of Terror were executed, including Saint-Just and Robespierre. The Terror took the lives of between 18,500 to 40,000 people.
After the Reign of Terror, Napoleon Bonaparte rose to be the emperor of France.