This chapter describes and explains the differentiated vertical and horizontal integration of macroeconomic policy in the EU, comprising both monetary and fiscal policy. Apart from their obvious political relevance for the EU, European monetary and fiscal policy offer rich and interesting data for the study of differentiated integration. First, monetary policy is one of the most integrated policies of the EU. It has moved, over time, from intergovernmental coordination to supranational centralization. The Economic and Monetary Union (EMU) introduced a supranational currency, the euro, and centralized monetary policy at the EU level. By contrast, fiscal policy has remained at the level of intergovernmental cooperation on member state budgetary policies. Only in the eurozone crisis have member states taken the decision to give up more sovereignty in this area. Second, macroeconomic policy is the most horizontally differentiated policy of the EU.