Vita Griffini Filii Conani is a critical edition, with facing English translation, of the Latin Life of Gruffudd ap Cynan. It has long been recognized that the surviving Welsh text is a translation of an original Latin life of Gruffudd ap Cynan, and it has always been assumed that the original Latin life had been lost. The main focus of this volume is on Peniarth MS, 434E which has been heavily annotated and corrected. The author shows that the annotation and correction was all intended to bring the text into line with the Welsh text, and that the underlying base text cannot be a translation of the Welsh text. The text edited here is that underlying, original text, and the author demonstrates that this text is not a translation of the Welsh text (as has always been thought) but a copy of the medieval Latin life of Gruffudd ap Cynan which predated the Middle Welsh translation. The effect of this discovery is extremely important for many aspects of medieval history, especially for medieval Wales but, given Gruffudd’s Irish and Norse origins, it can also cast a different light on Irish and Norse relations with Wales in the eleventh and twelfth centuries. The differences between the original Latin text and its Welsh translation raise all kinds of questions both for medieval historians and for students of translation literature. The book consists of an Introduction dealing with the significance of the text contained in Peniarth 434E, followed by the Latin text and translation, appendices and indexes.