The three-letter ISO code for the euro is EUR.
ISO 4217 assigns each currency a three-letter alphabetic code so banks, payment systems, traders, and financial databases can identify money unambiguously. In EUR, the first two letters, EU, refer to the European Union, while R is associated with the currency name.
The euro began as an electronic and accounting currency on 1 January 1999, with euro banknotes and coins entering circulation on 1 January 2002. It replaced national currencies in participating countries, although not every European Union member uses it. The code EUR is different from the euro symbol, €, and from the code XEU, which was used for the former European Currency Unit.
A common mix-up is USD, the ISO code for the United States dollar. JPY identifies the Japanese yen, while GBP identifies pound sterling. ISO codes are not the same thing as currency symbols, which can be ambiguous across countries.