This special issue explores the relationship between collective identities and the integration of core state powers, that is, the delegation of powers to a centralized institution in policy areas that are essential for the functioning of the modern state. In this introductory article we present the main conceptualizations of the contributions to the special issue that define our understanding of collective identities and core state powers. We discuss the multi‐level nature of collective identities and we discuss theoretical expectations over the link between collective identities and core state powers. Finally, we briefly present each of the contributions to the issue and discuss how they relate to the broad research goals, the special issue and to each other.