The abbey of Landevennec, an important foundation dedicated to the Celtic saint Guenole, was brought under the Benedictine rule by Louis the Pious in the ninth century. Its cartulary, compiled in the eleventh century, is an essential source for historians of medieval Brittany. The Latin charters were edited and published in 1886 by Rene-Francois-Laurent Le Men and Emile Ernault. Their preface provides a detailed description of the manuscript, including foliation, scripts, rubrication and an analysis of Breton personal and place names, whose changing orthography provides evidence for the development of the language over the centuries. The text includes a list of Landevennec’s abbots, charters documenting the expansion of the abbey’s holdings over the course of the tenth and eleventh centuries, and a list of the counts of Cornouaille. A complete index also provides translations of Breton terms into French.