This book introduces the concept of responsibility to the field of EU citizenship law by making three significant contributions to the field. Firstly, it examines all four protagonists in EU citizenship law (the individual, the home and host States, and the Union), providing a more holistic understanding of EU citizenship. Secondly, it highlights the importance of the home Member State and the continued significance of nationality. Finally, it presents the individual in a more nuanced light. It brings light and shade to a field where that can sometimes be lacking, allowing for a meaningful assessment of EU citizenship as it stands at a crossroads.