During the 10th century, the title imperatorappears in some Hispanic and Anglo-Saxon charters in reference to the sovereigns of Asturias and León and those of the new kingdom of England. Alphonse III of Asturias and León and Oswald of Northumbria are often considered the initiators or inspirers of these peculiar phenomena. The first Hispanic “imperial charters” seem to date back to the time of Alphonse III, while Oswald is described as imperator totius Britanniaein the Vita sancti Columbaeby Adomnán of Iona. This article aims to review the actual relevance of these two figures in the later use of imperial terminology. On the one hand, the only Alphonse’s 'imperial charters' whose authenticity is beyond doubt date from the time of his son Ordoño II, while,on the other hand, the dominant image of Oswald in 10th-century Britain was not that of Adomnán, but that reported by Bede, in which the imperial title does not appear