Sermones Contra Hereticos presents an edition and translation of a group of mostly unpublished Latin sermons which were originally preached in the context of the Albigensian Crusade of 1226 and during the fight against heresy in northern France in 1231. The nine extant sermon texts are unique in that they can be connected to specific preaching events for which the identity of the preacher, the time, and location, as well as the audience are known. The sermons were originally preached before academics at the University of Paris, to King Louis VIII of France at the start of his crusade in Bourges, at a procession in Paris in aid of the crusade army at the siege of Avignon, for the recruitment of additional crusaders, and at an episcopal synod at Laon and to laypeople at Bruyeres-et-Montberault in an attempt to ward off the spread of heretical beliefs. These texts provide us with an opportunity to tie particular strands of crusade ideology and doctrine to specific moments of the crusade movement and to the church's endeavours to counteract heresies by intensifying pastoral preaching. In addition, the texts can tell us a great deal about the way in which oral preaching was recorded and about the differences between the surviving textual record and the historical spoken word.