Albigenses, the collective name of various sects of heretics in the 12th and 13th centuries, who left the Catholic church and called themselves Catharists or Cathari (the pure). The word is derived from Albigeois (Albigesium), the territory of the viscount of Albi, the chief protector of the sects. The Avar against the Albigenses arose in consequence of the murder in 1208 of the papal legate Peter of Castelnau. Pope Innocent III. threw the blame on the heretical nobility of southern France, and in particular upon Raymond VI. of Toulouse, and had a crusade preached against them. Raymond averted the blow by submitting to the most humiliating conditions, and the crusading army, under the leadership of the legates Milo and Arnold, marched first against Raymond Roger, the visoount of Albi, Beziers, Carcassonne, and Rasez, whose land was devastated and given to Simon de Montfort. When Beziers, the capital of Roger, was taken by storm, 20,000 of the inhabitants were massacred. The army then (1211) turned against Raymond of Toulouse, who had again been excommunicated.

His land was also conquered, and in 1215 adjudged to Simon de Montfort. Raymond, however, supported by his subjects, continued a vigorous resistance to Simon, who in 1218 fell at the siege of Toulouse. A large portion of his territory was then reconquered by Raymond, and his son Raymond VII. even succeeded in forcing Amalric, the son of Simon, to a complete surrender. Louis VIII. of France, who was now prevailed upon by Pope Honorius to take arms against the Albigenses, died in November, 1226; but finally Raymond was compelled in 1229 to purchase relief from excommunication by ceding part of his territory to France, and by making his son-in-law, the brother-in-law of Louis IX. of France, heir to the remainder. Thus the Albigenses were left without a patron, and the inquisition was organized in 1229 by the council of Toulouse to complete their extermination. The name maintained itself, however, throughout the 13th century, not only in France, but also in upper Italy, Spain, and other countries, and disappeared at the beginning of the 14th century.

For the doctrine of the Albigenses see Catharists.