Do France and Germany lead the euro zone? We argue that the governments of these two countries jointly and successfully used institutional as well as ideational leadershipboth at the domestic as well as at the European levels when creating the Economic and Monetary Union in the 1980s and 1990s. During the euro zone crisis, however, the two respective governments mainly relied on institutional leadership, but neglected the ideational component of leadership. In consequence, member states only agreed upon lowest common denominator solutions, leaving the institutional setup of the Economic and Monetary Union incomplete. More ideational engagement by the French and German governments and the investment of political capital, in our view, are necessary for the adoption of more far-ranging substantial reforms. This would make the euro zoneand more generally the European integration projectmore resilient in the years to come.