The euro (symbol: €; currency code: EUR) is the official currency of 20 of the 27 member states of the European Union. This group of states is officially known as the euro area or, more commonly, the eurozone. The euro is divided into 100 euro cents.

The currency is also used officially by the institutions of the European Union, by four European microstates that are not EU members, and the British Overseas Territory of Akrotiri and Dhekelia, as well as unilaterally by Montenegro and Kosovo. Outside Europe, a number of special territories of EU members also use the euro as their currency.

The euro is used by 350 million people in Europe, and over 200 million people worldwide use currencies pegged to the euro. It is the second-largest reserve currency as well as the second-most traded currency in the world after the United States dollar. As of December 2019,^[update] with more than €1.3 trillion in circulation, the euro has one of the highest combined values of banknotes and coins in circulation in the world.

The name euro was officially adopted on 16 December 1995 in Madrid. The euro was introduced to world financial markets as an accounting currency on 1 January 1999, replacing the former European Currency Unit (ECU) at a ratio of 1:1 (US$1.1743 at the time). Physical euro coins and banknotes entered into circulation on 1 January 2002, making it the day-to-day operating currency of its original members, and by March 2002 it had completely replaced the former currencies.

Between December 1999 and December 2002, the euro traded below parity with the US dollar, but it has since traded near or above parity with the US dollar. On 13 July 2022, the two currencies briefly hit parity for the first time in nearly two decades, due in part to the Russian invasion of Ukraine. In the ten years ending 30 September 2025, the rate has averaged at about $1.00:€0.92.

The euro is managed and administered by the European Central Bank and the Eurosystem, composed of the central banks of the eurozone countries. As an independent central bank, the ECB has sole authority to set monetary policy. The Eurosystem participates in the printing, minting and distribution of euro banknotes and coins in all member states, and the operation of the eurozone payment systems.

Through their ratification of the 1992 Maastricht Treaty (or subsequent treaties of accession), most EU member states committed to adopt the euro upon meeting certain monetary and budgetary convergence criteria, although not all participating states have done so. Denmark has negotiated exemptions, while Sweden (which joined the EU in 1995, after the Maastricht Treaty was signed) turned down the euro in a 2003 non-binding referendum, and has circumvented its commitment to adopt the euro by not meeting the monetary and budgetary requirements. All nations that have joined the EU since 1993 have pledged to adopt the euro in due course. The Maastricht Treaty was amended by the 2001 Treaty of Nice, which closed the gaps and loopholes in the Maastricht and Rome Treaties.

The euro is the official currency of 43 countries and territories: