The European Economic and Monetary Union (EMU), or EU, is comprised of 27 member nations, 19 of whom have adopted the euro as their official currency. It is the single European currency, which replaced the national currencies of France, Germany, Spain, Italy, Greece, Portugal, Luxembourg, Austria, Finland, the Republic of Ireland, Belgium, and the Netherlands in 2002. Nineteen member states of the European Union now use the euro. The EU introduced the euro in 1999, and physical euro coins and paper notes were introduced in 2002. The symbol "EUR" is the abbreviation for the euro and it is the second most traded currency in the world, after the U.S. dollar.

EURO, monetary unit and currency of the European Union (EU). It was introduced as a noncash monetary unit in 1999, and currency notes and coins appeared in participating countries on January 1, 2002. After February 28, 2002, the euro became the sole currency of 12 EU member states, and their national currencies ceased to be legal tender. Other states subsequently adopted the currency. The euro is represented by the symbol €.

The euro’s origins lay in the Maastricht Treaty (1991), an agreement among the then 12 member countries of the European Community (now the European Union)—United Kingdom, France, Germany, Italy, Ireland, Belgium, Denmark, the Netherlands, Spain, Portugal, Greece, and Luxembourg—that included the creation of an economic and monetary union (EMU). The treaty called for a common unit of exchange, the euro, and set strict criteria for conversion to the euro and participation in the EMU. These requirements included annual budget deficits not exceeding 3 percent of gross domestic product (GDP), public debt under 60 percent of GDP, exchange rate stability, inflation rates within 1.5 percent of the three lowest inflation rates in the EU, and long-term inflation rates within 2 percent. Although several states had public debt ratios exceeding 60 percent—the rates topped 120 percent in Italy and Belgium—the European Commission (the executive branch of the EU) recommended their entry into the EMU, citing the significant steps each country had taken to reduce its debt ratio.

Supporters of the euro argued that a single European currency would boost trade by eliminating foreign exchange fluctuations and reducing prices. Although there were concerns regarding a single currency, including worries about counterfeiting and loss of national sovereignty and national identity, 11 countries (Austria, Belgium, Finland, France, Germany, Ireland, Italy, Luxembourg, the Netherlands, Portugal, and Spain) formally joined the EMU in 1998. Britain and Sweden delayed joining, though some businesses in Britain decided to accept payment in euros. Voters in Denmark narrowly rejected the euro in a September 2000 referendum. Greece initially failed to meet the economic requirements but was admitted in January 2001 after overhauling its economy.