European citizenship, although derived from the nationalities of the Member States, came to play a significant independent role in reforming European constitutionalism in unanticipated ways by undermining some of the key assumptions underlying the notions of citizenship, equality and democratic accountability. Instead of lingering merely as a super-structure atop Member State nationalities, it instead reshuffles the constitutional basics and not all Europeans emerge as winners as a result. This brief Article provides an introductory background for the Special Section on EU citizenship and rights of European Papers, Vol. 3, 2018, No. 3 and outlines some of the core tensions which EU citizenship brings to light.