What is the euro zone?

The euro is the single currency shared by (2009) 16 of the European Union's Member States, which together make up the euro area.
The introduction of the euro in 1999 was a major step in European integration. It has also been one of its major successes: around 329 million EU citizens now use it as their currency and enjoy its benefits, which will spread even more widely as other EU countries adopt the euro.

The euro is not the currency of all EU Member States. Two countries (Denmark and the United Kingdom) agreed an ‘opt-out’ clause in the Treaty exempting them from participation, while the remainder (many of the newest EU members plus Sweden) have yet to meet the conditions for adopting the single currency. Once they do so, they will replace their national currency with the euro.

The countries currently using the euro are (by order of adoption):
- Belgium, Germany, Ireland, Spain, France, Italy, Luxembourg, the Netherlands, Austria, Portugal and Finland - all in 1999
- Greece - 2002
- Slovenia - 2007
- Cyprus and Malta - 2008
- Slovakia - 2009