The European Union’s (EU) fundamental principles of free movement of persons and non-discrimination have long challenged the traditional closure of the welfare state. Whereas the relationship between the EU and the welfare state appeared largely reconciled before the grand enlargement of 2004, economic downturn and politicisation question the nexus anew. This collection explores the current dynamics, scope and limits of free movement and welfare equal treatment for EU citizens on the move. The different contributions bring together the normative, legal and political developments and about-turns which dynamically square the circle of pan-European social solidarity. The collection covers the new politics of EU cross-border welfare but also the structuring role of the European Court of Justice. It includes the political economy of free movement as well as its outputs and outcomes in selected member states. Finally, it analyses the mechanisms that activate attitudinal polarisation on intra-EU migration and welfare.