Ri·che·lieu 
(rĭshə-l′, rē-shə-lyœ), Duc de. Title of Armand Jean du Plessis. 1585-1642.
(rĭshə-l′, rē-shə-lyœ), Duc de. Title of Armand Jean du Plessis. 1585-1642. French cardinal and politician. As chief minister of Louis XIII he worked to strengthen the authority of the monarchy and directed France during the Thirty Years' War (1618-1648).