Paolo Giovio’s Descriptio Britanniae, Scotiae, Hyberniae et Orchadum presents several problems for the historian of early modern Ireland. Published in 1548, but composed for the most part during the early 1540s, it offered a comparatively detailed portrait of Irish geography, culture and politics to an international audience whose appetite for Irish affairs had been whetted by the recent Henrician Reformation. Yet the text offers scant commentary on Irish politics; its geographical information is often confused; its ethnography is evocative but rarely moralising; and its focus on Ulster and the lifestyle of Conn O’Neill is suggestive but tantalisingly so. The author’s sources are as obscure as his intentions. Nevertheless, Giovio’s text was still being read and cited by leading European and even Irish authors up to a hundred years later. It was a seminal treatment of Ireland and the Irish that found few parallels in international print-houses until the gradual emergence of the writings of Giraldus Cambrensis towards the end of the sixteenth century. This article sets the Descriptio in the twin context of early modern geographical humanism and the international fallout of the Henrician Reformation.