The Thermidorian Reaction was a coup d'état within the French Revolution against the leaders of the Jacobin Club who had dominated the Committee of Public Safety. It was triggered by a vote of the National Convention to execute Maximilien Robespierre, Louis Antoine de Saint-Just, and several other leading members of the revolutionary government. This ended the most radical phase of the French Revolution.

The name Thermidorian refers to 9 Thermidor Year II (27 July 1794), the date according to the French Republican Calendar when Robespierre and other radical revolutionaries came under concerted attack in the National Convention. Thermidorian Reaction also refers to the remaining period until the National Convention was superseded by the Directory; this is also sometimes called the era of the Thermidorian Convention. Prominent figures of Thermidor include Paul Barras, Jean-Lambert Tallien, and Joseph Fouché.

Thermidor represents the final throes of the Reign of Terror. With Robespierre the sole remaining strong-man of the Revolution following the assassination of Jean-Paul Marat (13 July 1793), and the executions of Jacques Hébert (24 March 1794), Georges Danton and Camille Desmoulins (5 April 1794), his apparently total grasp on power became in fact increasingly illusory, especially insofar as he seemed to have support from factions to his right. His only real political power at this time lay in the Jacobin Club, which had extended itself beyond the borders of Paris and into the country as a network of "Popular Societies". In addition to widespread reaction to the Reign of Terror, Robespierre's tight personal control of the military, his distrust of military might and of banks, and his opposition to supposedly corrupt individuals in government, made him the subject of a number of conspiracies.

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