It refers to the short but bloody period in French history that began in 1793 and ended July 1794. During this time revolutionary leader Maximilien Robespierre (1758–1794)led a tribunal that arrested, tried, and put to death more than 17,000 people—most of them by guillotine.

In the reforms that followed the 1789 Oath of the Tennis Court and the capture of the Bastille, France was transformed into a constitutional state, and French subjects became French citizens. An elected legislature (the Constituent Assembly) was given control of the government. Robespierre was elected first deputy from Paris and was the leader of the radical popular party. In this new era, those who had been associated with the old regime or those who opposed the French Revolution became the subjects of persecution. In January 1793 King Louis XVI (1754–1793) and his wife, Marie Antoinette (1755–1793), were executed, beginning the Reign of Terror that saw thousands more (mostly those who had made up the powerful first and second estates) suffer a similar fate at the hands of the revolutionaries. To escape certain death, many fled the country; this included top-ranking military officials, which made room for the rapid advancement of young military officers such as Napoleon Bonaparte (1769–1821).

The Reign of Terror ended on July 28, 1794, when Robespierre himself was put to death. As he gained power and influence, the revolutionary leader also had become increasingly paranoid, even putting two of his friends to death in 1794. He was overthrown on July 27 by the Revolution of 9th Thermidor and the next day died by guillotine.