The rights and duties associated with the concept of citizenship are a central aspect of the process of identity-building and state formation. This book explores the origin and evolution of the concepts of citizenship and identity in Ireland from a broadly historical perspective, tracing their development in terms of rights and duties, from classical times, through the medieval period and the era partition in Ireland, to the present difficulties surrounding Brexit and the refugee crisis. Ireland's population has, by the standards of states elsewhere in Europe, remained fairly stable and homogeneous, at least until recently. The present refugee crisis presents Ireland with the prospect of asylum seekers and other migrants with very different cultures, traditions and senses of identity arriving on a scale quite unknown previously, with consequent difficulties surrounding their admission and integration into Irish society. An examination of how the basic criteria and conditions under which citizenship has been conferred here compares with those for granting citizenship in other parts of Europe suggests that evolution of citizenship concepts in Ireland has more generally accorded with familiar European patterns of development. Depending on how future relations between the UK and the EU are agreed following Brexit, however, the island of Ireland faces the prospect of immigrants from other EU member states enjoying what are in effect the rights of citizens in the Republic of Ireland but no such rights in Northern Ireland.