This work reprints the definitive 1952 edition of two of the most significant works in the corpus of Celtic-Latin literature, St Patrick's "Confessio" and his "Epistola ad milites Corotici". These texts by the national apostle are the only texts in any language known to survive from fifth-century Ireland and offer primary evidence concerning the life, personality and achievements of St Patrick. They will be of interest to historians, theologians, archaeologists, geographers, linguists, Celticists and others attempting to shed light on those obscure times. The book is an ancillary volume to the Royal Irish Academy's "Dictionary of Medieval Latin from Celtic Sources" project, whose main publications are detailed at http://journals.eecs.qub.ac.uk/DMLCS.