The eurozone (EZ), officially called the euro area, is a group of 19 member states of the European Union (EU) that have fully implemented the Economic and Monetary Union of the European Union and have thus adopted the euro () as their primary currency and sole legal tender. The monetary authority of the eurozone is the Eurosystem. Eight members of the European Union continue to use their own national currencies, although most of them have agreed to adopt the euro in the future.

The eurozone consists of Austria, Belgium, Cyprus, Estonia, Finland, France, Germany, Greece, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Portugal, Slovakia, Slovenia, and Spain. Croatia will become the 20th member on 1 January 2023. Other EU states (except for Denmark) are obliged to join once they meet the criteria to do so. No state has left, and there are no provisions to do so or to be expelled.Among non-EU member states, Andorra, Monaco, San Marino, and Vatican City have formal agreements with the EU to use the euro as their official currency and issue their own coins. In addition, Kosovo and Montenegro have adopted the euro unilaterally. These countries, however, do not officially form part of the eurozone and have representation neither in the European Central Bank (ECB) nor in the Eurogroup.The ECB, which is governed by a president and a board of the heads of national central banks, sets the monetary policy of the zone. The principal task of the ECB is to keep inflation under control. Though there is no common representation, governance or fiscal policy for the currency union, some co-operation does take place through the Eurogroup, which makes political decisions regarding the eurozone and the euro. The Eurogroup is composed of the finance ministers of eurozone states, but in emergencies, national leaders also form the Eurogroup.

Since the financial crisis of 20072008, the eurozone has established and used provisions for granting emergency loans to member states in return for enacting economic reforms. The eurozone has also enacted some limited fiscal integration: for example, in peer review of each other's national budgets. The issue is political and in a state of flux in terms of what further provisions will be agreed for eurozone change.

The European Exchange Rate Mechanism (ERM) II is a system introduced by the European Economic Community on 1 January 1999 alongside the introduction of a single currency, the euro (replacing ERM 1 and the euro's predecessor, the ECU) as part of the European Monetary System (EMS), to reduce exchange rate variability and achieve monetary stability in Europe.

After the adoption of the euro, policy changed to linking currencies of EU countries outside the eurozone to the euro (having the common currency as a central point). The goal was to improve the stability of those currencies, as well as to gain an evaluation mechanism for potential eurozone members. As of July 2021, three currencies participate in ERM II: the Danish krone, the Croatian kuna and the Bulgarian lev.