Adomnán (c.625–704) was ninth abbot of the monastery on Iona off the Scottish coast. Adomnán came from what is now County Donegal. He was one of the most significant churchmen and intellectuals of the seventh century. The copying and re-copying of his written works meant that, in medieval times, his reputation spread widely on the Continent. He was, in modern parlance, an 'all-rounder': monk, priest, manager, writer, historian, lawmaker and diplomat, to name just a few things. He was the author of one of the first laws, anywhere, for the protection of non-combatants in times of conflict, and compiled an exegetical 'guide-book' to the 'sites' of the Holy Land – the oldest surviving text of its kind from anywhere in Western Europe. He also wrote a major hagiographical 'Life' of his predecessor and distant relative Columba. So powerful and influential a text was that book that it all but shoved Adomnán himself out of the limelight, in favour of his illustrious forerunner. Although much has been written about individual aspects of Adomnán's career, this is the first study to outline the totality of his life and reputation – in so far as we can know it!