MONTFORT, the name of a famous French family long seated at Montfort 1'Amauri, near Paris, descended from a certain William, a descendant of the counts of Flanders, who flourished during the latter part of the 10th century, and who built a castle at Montfort l'Amauri. Until 1209, when Simon IV. took the title of count, William and his successors were known as barons de Montfort. This Simon IV. de Montfort (c. 1160- 1218), a son of Simon III. (d. 1181), is chiefly known for the very active part which he took in the crusade against the Albigenses. Twice he went to Palestine as a crusader, and in 1209, answering the call of Pope Innocent III., he joined the host which marched against the enemies of the Church in Languedoc. He became vicomte of Beziers and of Carcassonne, and was soon the leader of the crusaders. He took place after place, defeated Raymond VI., count of Toulouse, at Castelnaudary, and about a year later (September 1213) gained a victory over Raymond's ally, Peter II., king of Aragon, under the walls of Muret. Simon then turned his attention to administering and organizing Languedoc. After a lively discussion in the Lateran Council of 1215, the pope, somewhat reluctantly, confirmed him in the possession of the greater part of the lands of the count of Toulouse, and after two more years of warfare he was killed whilst besieging the city of Toulouse on the 25th of June 1218. The count's eldest son, Amauri de Montfort (1192-1241), was unable to hold his own, although Philip Augustus sent some troops to his assistance in 1222. He abandoned his interests in the south of France in favour of the new king Louis VIII., and in 1239 he went on crusade to the Holy Land, dying soon afterwards at Otranto. In 1230 Amauri was made constable of France. Simon IV. had a brother, Guy de Montfort (d. 1228), who shared his military exploits both in Asia and in Europe, and who was afterwards employed by Louis VIII. to negotiate with the pope at Rome. He was killed before Vareilles on the 31st of January 1228. In 1294 Yolande (d. 1322), the heiress of the Montforts, married Arthur II., duke of Brittany, and the county of Montfort became part of this duchy. Their son, John, count of Montfort, claimed Brittany in opposition to Charles, count of Blois, and at length secured the duchy. Except for one interval his descendants held it until it was united with the French crown at the end of the 15th century.
See A. Molinier, Catalogue des actes de Simon et d'Amaury de Montfort (1873); and C. Douais, La Soumission de la vicomte de Carcassonne par Simon de Montfort et la croisade centre Raimond VI. (1884).
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)