The Champ de Mars massacre took place on 17 July 1791 in Paris at the Champ de Mars against a crowd of republican protesters amid the French Revolution. Two days before, the National Constituent Assembly issued a decree that King Louis XVI would retain his throne under a constitutional monarchy. This decision came after Louis and his family had unsuccessfully tried to flee France in the Flight to Varennes the month before. Later that day, leaders of the republicans in France rallied against this decision, eventually leading royalist Marquis de Lafayette to order the massacre.