Louis De Rouvroi Saint-Simon, duke de, a French writer of memoirs, born Jan. 16, 1675, died in Paris, March 2, 1755. Under the direction of his mother, Charlotte de l'Aubespine, he became proficient in Latin, German, and history. He served at the siege of Namur in 1691, and subsequently distinguished himself in various campaigns. In 1695 he married Gabrielle de Durfort, daughter of the marshal de Lorges. In 1702, failing to be promoted, he retired from the army. He was prominent at the French court, and was a strenuous opponent of the Jesuits. In 1704 he proposed to end the Spanish war of succession by giving the Spanish Low Countries to Austria and a portion of the Spanish possessions in Italy to a prince of the house of Savoy with the title of king; and his suggestion was to some extent adopted as a basis for the treaty of peace of Utrecht. After the death of Louis XIV. (1715) he aided the duke of Orleans in obtaining the regency, and was a member of the council. In 1721 he negotiated at Madrid the marriage between the infanta of Spain and Louis XV. On his return to Paris he found the cardinal Dubois, whom he had always opposed, more powerful than ever, and the legitimated bastards of Louis XIV. partly reinvested with royal dignities.

Consequently he broke off his relations with the government until after the death of Dubois, shortly before that of the regent, upon which he retired to his estates. His Mémoires, which subsequently attained unusual celebrity on account of their boldness of expression and pungent satire, were removed to the public archives, and only Voltaire, Marmontel, Mme. du Deffand, and a few others were permitted to read them. Garbled extracts and editions were published in 1788 and 1791; the first authentic and complete series appeared in 1829-'30, and a greatly improved edition was published by Cheruel (20 vols., 1856-'9; abridged English translation by Bayle St. John, 4 vols., London, 1857; new ed., 3 vols., 1875). Among his posthumous papers were found hundreds of letters of the duke of Orleans, unpublished essays of Montaigne, and other valuable manuscripts, of which a full catalogue was obtained from the public archives by Armand Baschet, who published in 1874 Le due de Saint-Simon, son cabinet et l'histoire de ses manuscrits.