Louis François Armand du Plessis, duc de Richelieu (March 13, 1696 - August 8, 1788) was a marshal of France and a grandnephew of Cardinal Richelieu.

He was born in Paris. Apart from his reputation as a man of exceptionally loose morals, he attained, in spite of a deplorably defective education, distinction as a diplomatist and general. As ambassador to Vienna (1725-1729) he settled in 1727 the preliminaries of peace; in 1733-1734 he served in the Rhine campaign .

His real public career began ten years later. He fought with distinction at Dettingen and Fontenoy, where he directed the grapeshot upon the English columns, and three years afterwards he made a brilliant defence of Genoa; in 1756 he expelled the English from Minorca by the capture of the San Felipe fortress ; and in 1757-1758 he closed his military career by those pillaging campaigns in Hanover which procured him the sobriquet of "Petit Père de la Marauds."

After the wars he plunged again into court intrigue, favoured the comtesse du Barry and supported his nephew the duc d'Aiguillon. Louis XVI, however, was not favorably inclined to him. In his early days he was thrice imprisoned in the Bastille: in 1711 at the instance of his stepfather, in 1716 in consequence of a duel, and in 1719 for his share in Alberoni's conspiracy against the regent Orleans.

He was thrice married: first, against his will, at the age of fourteen to Anne Catherine de Noailles; secondly, in 1734, by the intrigues (according to the witty Frenchman's own account) of Voltaire, to Marie Elisabeth Sophie, Mademoiselle de Guise; and thirdly, when he was eighty-four years old, to an Irish lady.

Marshal Richelieu's Memoires, published by JL Soulavie in nine volumes (1790), are partially spurious. See H Noel Williams, The Fascinating Duc de Richelieu (1910).