This special issue explores how Europe’s Union is tested though crises but also faces explicit contestation in troubled times. Crises are ‘open moments’ that impact on rulers and ruled, testing existing paradigms, policies, politics, institutional roles and rules. The papers in this special issue test the resilience of the Union in crisis conditions, the post-functionalist interpretation of contemporary integration, the legacy of the crisis for politics and institutions in Europe and the impact of the crisis on key bilateral relations. Four thematic issues are addressed: the resilience of the EU, multilevel politics, patterns of continuity and change and the relationship between the whole (EU) and the member states.