Henri Coiffier de Ruzé, Marquis de Cinq-Mars (1620 – September 12, 1642) was a favourite of King Louis XIII of France who led the last and most nearly successful of the many conspiracies against the king's powerful first minister, the Cardinal Richelieu.
Cinq-Mars was the son of Marshal Antoine Coiffier-Ruzé, marquis d'Effiat, a close friend of Richelieu, who took the boy under his protection on his father's death in 1632.
In 1639 Louis XIII had no favourite. Richelieu had introduced the young Cinq-Mars to Louis, hoping the king would take Cinq-Mars as a lover, apparently with success: Tallemant des Réaux in his Historiettes (chapter on Louis XIII) cites Fontrailles, who relates a scene where the king and his minion Cinq-Mars went to bed together. The cardinal believed he could easily control Cinq-Mars. Instead, Cinq-Mars pressed the king for important favours and tried to convince the king to have Richelieu executed. Cinq-Mars brought some French nobility into revolt, but the effort failed. He also tried to get support for the rebellion from Philip IV, the king of Spain; Richelieu's spy service caught him doing so. Richelieu then had Cinq-Mars imprisoned and beheaded in the Place des Terreaux in Lyon. Tallemant relates that the king showed no emotions concerning the execution: he said "Je voudrais bien voir la grimace qu'il fait à cette heure sur cet échafaud" (I would like to see the grimace he is now making on that scaffold).
Alfred de Vigny wrote a novel Cinq-Mars, inspired by the story of the marquis, and published in 1826. Charles Gounod wrote an opera of the same name which premiered on April 5, 1877.
For historical accounts, consult Basserie, La conjuration de Cinq-Mars (Paris, 1896) and Bazin, Histoire de France sous Louis XIII (Paris, 1846).