Monsieur Philippe I, Duke of Orléans (21 September 1640 – 9 June 1701) was the younger son of King Louis XIII of France and Anne of Austria, and the younger brother of King Louis XIV. He was the founder of the House of Orléans, a cadet branch of the ruling House of Bourbon.
Styled Duke of Anjou from birth, Philippe became Duke of Orléans upon the death of his uncle Gaston in 1660. He was also granted the dukedoms of Valois, Chartres and Nemours. Known as le Petit Monsieur or simply Monsieur, Philippe was a distinguished military commander and took part in the War of Devolution and the Franco-Dutch War, the latter of which saw his victory over William of Orange at the Battle of Cassel. Through careful personal administration, he greatly augmented the fortunes of the House of Orléans, which rivalled that of the Bourbons.