Françoise Athénaïs marquise de Montespan

Montespan, Françoise-Athénaïsde Rochechouart, marquise de (1640-1709), became Louis XIV's mistress in 1667, ousting Louise de la Vallière. She bore him seven children, later legitimized, before losing her position in the late 1670s. She was a patron of Racine and Boileau, but was also suspected of involvement in black magic and poisoning [see Poisons, Affaire Des].

The noun has one meaning:

Meaning #1: French noblewoman who was mistress to Louis XIV until he became attracted to Madame de Maintenon (1641-1707)
  Synonyms: Montespan, Francoise-Athenais de Rochechouart