This study focuses on the creation of both British ethnic or ‘national’ identity and Brittonic regional/dynastic identities in the Roman and early medieval periods. It is divided into two interrelated sections which deal with a broad range of textual and archaeological evidence. Its starting point is an examination of Roman views of the inhabitants of the island of Britain and how ethnographic images were created in order to define the population of Britain as 2 barbarians who required the civilising influence of imperial conquest. The discussion here seeks to elucidate, as far as possible, the extent to which the Britons were incorporated into the provincial framework and subsequently ordered and defined themselves as an imperial people. This first section culminates with discussion of Gildas’s De Excidio Britanniae. It seeks to illuminate how Gildas attempted to create a new identity for his contemporaries which, though to a certain extent based on the foundations of Roman-period Britishness, situated his gens uniquely amongst the peoples of late antique Europe as God’s familia. The second section of the thesis examines the creation of regional and dynastic identities and the emergence of kingship amongst the Britons in the late and immediately post-Roman periods. It is largely concerned to show how interaction with the Roman state played a key role in the creation of early kingships in northern and western Britain. The argument stresses that while there were claims of continuity in group identities in the late antique period, the socio-political units which emerged in the fifth and sixth centuries were new entities. Indeed, it will emphasise that there was no return or re-emergence of a primitive form of kingship influenced by deep-seated notions of Celtic-ness. Rather, this study demonstrates that regional Brittonic groups participated in the broader cultural and socio-political transformations that mark out the late antique period across the western provinces of the failing Roman empire.