Duke of Richelieu was a title in the peerage of France. It was created on 26 November 1629 for cardinal Richelieu who, as a clergyman, had no issue to pass it down to. It instead passed to his great-nephew, Armand Jean de Vignerot, grandson of his elder sister Françoise (1577-1615), who had married René de Vignerot, lord of Pontcourlay († 1625).
Armand Jean de Vignerot added the cardinal's surname of du Plessis to his own, took the cardinal's coat of arms (d'argent à trois chevrons de gueules « sans meslange d'aulcunes autres ») and received the titles of duke of Richelieu and peer of France by letters patent in 1657.
Two new reversions of the title occurred in 1822 and 1879. In effect, Armand Emmanuel du Plessis, duc de Richelieu died without an heir, but he gained permission for the title of duke of Richelieu to pass to the son of his half-sister Simplicie, daughter of Antoine-Pierre de La Chapelle de Saint-Jean de Jumilhac, with reversion to the descendents of his younger brother should he die without a male heir - meaning that, in effect, the title passed to his nephew.