Adomnán of Iona is best known as the author of The Life of Saint Columba but his other extensive work ‘On the Holy Place’ was also widely read in the Middle Ages. It purports to be an account of the Holy Land and Constantinople given him by a Gallic bishop Arculf. This book contains the earlies surviving textual account of Mu’awiya, the fifth caliph of Islam, whose activities take up a chapter of the work. In this talk I suggest why Adomnán was interested in Mu’awiya and what use he put him to.