While the answer may seem obvious – they use the euro in Europe – it’s actually not. They do use it in Europe, but not in all of Europe, and not even in the whole of the European Union. As of 2009, 16 of the 27 EU member countries have adopted the euro as their national currency. It began in 1999 with Belgium, Germany, Ireland, Spain, France, Italy, Luxembourg, the Netherlands, Austria, Portugal, and Finland switching their currencies over. Greece followed suit in 2001, Slovenia in 2007, Cyprus and Malta in 2008, and Slovakia in 2009. Combined, these areas are called the “eurozone.” A country must meet strict criteria in order to qualify for the euro standard. That’s why countries gradually join the eurozone instead of all at once.
329 million people living in these 16 countries use the euro daily. Additionally, some neighbor countries and former colonies use the euro as an unofficial currency as well. For these reasons, the euro has become the second most important international currency just behind the dollar.