Montfort

The House of Montfort-l'Amaury was an Ile-de-France noble house, a cadet branch of Hainaut's counts. Hugh Capet enfeoffed Guillaume de Montfort; his heirs built Montfort-l'Amaury, named for Amaury I. Simon I married Agnes of Evreux, gaining the county; his daughter Bertrade, wed to Fulk IV, Philip I carried off and married.

Simon III's marriage to Leicester heiress Amicia opened the family's English career. His son Simon IV led the Albigensian Crusade from 1209, became count of Toulouse and fell there in 1218; his son Amaury ceded those claims to Louis VIII in 1224.

The younger Simon, earl of Leicester, married King John's daughter Eleanor and led revolt against Henry III, capturing him at Lewes in 1264 and falling at Evesham in 1265; Montfort-l'Amaury passed to the House of Dreux. The name survived through Yolande, wed to Arthur II of Brittany in 1292: their John of Montfort won the Breton succession at Auray in 1364, his line ruling Brittany until the male line died with Francis II in 1488.