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Duke of Mayenne (duc de Mayenne) is a title created for a cadet branch of the House of Guise. It subsequently passed by marriage to the Gonzaga in 1621, who sold it to Cardinal Mazarin in 1654; he bestowed it on his niece, Hortense Mancini in 1661. Due to the terms of the entailment on the title, it became extinct in 1781, but it is still claimed by the Sovereign Prince of Monaco, a descendant of Hortense.