2013 has been designated the 'European Year of Citizens'. It marks the 20th anniversary of the entry into force of the Maastricht Treaty, which first introduced European Union citizenship. In the midst of a major socioeconomic crisis, accompanied by solid trends of declining support for the European Union and the resurgence of nationalisms in many EU member states, EU citizenship offers a countermodel capable of reinforcing citizens’ resilience and their feeling of belonging to a community of Europeans. Yet, while the citizenship status promises an important set of rights and opportunities for... all EU citizens, challenges continue to persist. This policy review critically discusses the advances in the 'co-creation' of European Union citizenship over the past 20 years, while highlighting the manifold remaining obstacles to the exercise of citizenship rights in the EU. It draws on the key research findings of 15EU-funded social sciences and humanities research projects with a bearing for understanding the genesis and evolution of EU citizenship. On the basis of a sound synthesis of these findings, the Review formulates a set of policy implications highlighting, among others, the need to involve citizens to a larger extent in EU policy-making and to reinforce the social dimension of EU citizenship.