New and definitive edition of Irish martyrology reveals its European origins. The martyrology edited here, for the first time since the nineteenth century, derives from a rich variety of sources and has a fascinating history. While it draws on Danish and Irish manuscripts from the twelfth and thirteenth centuries, the editor argues that its layers of Metz and Cologne saints were not added either in Ireland, as has been previously thought, or in Denmark, but rather in the Benedictine monasteries at these two medieval German cities. The presence in both manuscripts of a layer of Irish saints indicates that Irish activity on the Continent had a bearing on the early history of the text, and detailed investigations have led to the monasteries in Metz and Cologneas being those in which the text originated about the year 1000 AD. The text is accompanied with full introduction, notes, and indices. Padraig O Riain is Professor Emeritus of Early and Medieval Irish at University College Cork.