Descended from a noble family, educated in a convent at Caen, and royalist by sentiment, yet susceptible also to the ideals of the Enlightenment, Corday was living with an aunt in Caen when it became a centre of the “federalist” movement against the National Convention after the expulsion of the Girondins in May–June 1793. Inspired especially by Charles Barbaroux among the Girondin refugees, she left for Paris to work for the Girondin cause.

There Corday solicited an interview with Marat because of the influence of his newspaper over the masses, and on July 13, 1793 she was finally admitted to his presence while he was in his bath. She named dissidents in Normandy; he noted them and assured her that they would be guillotined. She then drew a knife from under her dress and stabbed him through the heart. Arrested on the spot, she was tried and convicted by the Revolutionary Tribunal (July 16–17) and forthwith guillotined on the Place de la Révolution.