Economic and Monetary Union of the European Union

The economic and monetary union of the European Union is a set of policies intended to converge the economies of member states through three progressive stages, the third and final of which allows a country to formally adopt the euro as its currency and is largely synonymous with membership in the eurozone. To enter the third stage a country must satisfy the euro convergence criteria, which include at least two years of participation in the European Exchange Rate Mechanism and keeping its currency within limited deviation from its target rate against the euro. The framework applies to all European Union member states, and every new member commits through its accession treaty to eventually adopt the euro once it meets the convergence criteria. Twenty one member states have adopted the euro as of the most recent accession, Bulgaria, while Denmark holds a legal opt out from the third stage predating the euro's introduction, and several other states retain their own currencies while working toward the convergence criteria. The framework traces to the Maastricht Treaty of 1992, and its central institutions include the European Central Bank, the European Commission and the Council of the European Union.