The Albigensian Crusade, which forms the main subject of William of Puylaurens' Chronicle, was a defining episode in the history of France. Launched in 1209 by Pope Innocent III, it was directed against the aristocracy of southern France (especially the Counts of Toulouse) who were accused of protecting heresy, and especially Catharism, a dualist heresy which represented a major threat to the Catholic Church. The Crusade ended in 1229 with the defeat of Count Raymond VII of Toulouse. It was followed in the 1230s by the establishment of the Papal Inquisition against heresy. The long-term outcome of the Crusade was the defeat of Catharism, and the establishment of French Royal power in the region. William of Puylaurens' Chronicle, here translated into English for the first time, is one of the main contemporary accounts of these events. It describes heresy in the south of France in the early 13th century; provides a narrative of the Crusade; and then outlines the growth of the Inquisition and the sustained attack on heresy which followed, including the siege of the Cathar fortress of Montségur in 1243-44. This translation is accompanied by an introduction, full notes, appendices, and a bibliography. W.A. SIBLY is a former Domus Exhibitioner in Classics at Balliol College, Oxford; M.D. SIBLY read history at Corpus Christi College, Cambridge. They have also translated Peter of Les Vaux de Cernay's History of the Albigensian Crusade (also published by Boydell & Brewer).