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 1632, Louis had no favourite. Richelieu had introduced the young Cinq-Mars to Louis, hoping Louis would take Cinq-Mars as a lover. Apparently with success: Tallemant des Réaux in his Historiettes cites Fontrailles, who relates a scene where the king and his minion Cinq-Mars went to bed together (Historiettes, Chapter on Louis XIII). The cardinal believed Cinq-Mars was easy to control. 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. Richelieu had him imprisoned and then beheaded in Lyon. Tallemant relates that the king showed no emotions concerning the execution: he said "Je voudrois bien voir la grimace qu'il fait à cette heure sur cet échafaud" (I would like to see the face he is now making on the scaffold).
For historical accounts, consult Basserie, La conjuration de Cinq-Mars, (Paris, 1896); Bazin, Histoire de France sous Louis XIII, (Paris, 1846).