With the launch of the Single Supervisory Mechanism and Single Resolution Mechanism, the European Banking Union is inching toward completion. We have witnessed a proliferation of new institutions, policies, and guidelines. Some of these institutions and instruments follow on trends preceding the Eurozone sovereign debt crisis, while others constitute major breakthroughs on the path to a truly supranational regime in banking supervision. Their ongoing operational consolidation raises important questions: How do these elements relate to each other and do they amount to a coherent institutional design? Which actors were influential in designing the Banking Union? What factors have shaped the preferences of the non-Eurozone EU member states that need to decide whether to opt in or stay out of the Banking Union? This panel provides a state of the art overview of one of the most important breakthroughs in European integration in the last decade, which has the potential to reinforce the division between the “ins” and the “outs” in European banking sector governance. The first two papers (Botta and Kudrna, Fleisher) review the origins of the Banking Union design within the EU legislative institutions and its position in the EU’s emerging multi-level accountability framework. The next set of papers (Hungin, Donnelly) analyze the transformed role of the European Central Bank, which is at the core of the Banking Union architecture. The final two papers evaluate the incentives for Sweden (Spendzharova and Bayram) and Lithuania (Skuodis and Kuokštis) to join the European Banking Union.