The euro (currency sign: €; currency code: EUR) is the official currency of 16 out of 27 member states of the European Union (EU). The states, known collectively as the Eurozone are: Austria, Belgium, Cyprus, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, Malta, the Netherlands, Portugal, Slovakia, Slovenia, and Spain. The currency is also used in a further five European countries, with and without formal agreements and is consequently used daily by some 327 million Europeans.

As of November 2008[update], with more than €751 billion in circulation (the equivalent of about US$ 953 billion), the euro is the currency with the highest combined value of cash in circulation in the world, having surpassed the U.S. dollar. Based on IMF estimates of 2008 GDP and purchasing power parity among the various currencies, the Eurozone is the second largest economy in the world.

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. Physical coins and banknotes entered circulation on 1 January 2002.

The euro is managed and administered by the Frankfurt-based European Central Bank (ECB) 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 notes and coins in all member states, and the operation of the Eurozone payment systems.

The 1992 Maastricht Treaty obliges all EU member states to adopt the euro upon meeting certain monetary and budgetary requirements, however, not all states have done so. The United Kingdom and Denmark negotiated exemptions. while Sweden turned down the euro in a 2003 referendum, and has circumvented the obligation to adopt the euro by not meeting the monetary and budgetary requirements. All nations that have joined the EU since the 1993 have pledged to adopt the euro in due course.

The coins are issued in €2, €1, 50-cent, 20-cent, 10-cent, 5-cent, 2-cent, and 1-cent denominations. In order to avoid the use of the two smallest coins, some cash transactions are rounded to the nearest five cents in the Netherlands (by voluntary agreement) and in Finland (by law).

Notes are issued in €500, €200, €100, €50, €20, €10, €5. Each banknote has its own colour and is dedicated to an artistic period of European architecture. The front of the note features windows or gateways while the back has bridges. Care has been taken so that the architectural examples do not represent any actual existing monument, so as not to induce jealousy or controversy in the choice of monuments. Some of the highest denominations such as the €500 are not issued in all countries, though they remain legal tender throughout the Eurozone.

After the introduction of the euro, its exchange rate against other currencies fell heavily, especially against the U.S. dollar. From an introduction at US$1.18/€, the euro fell to a low of $0.8228/€ by 26 October 2000. After the appearance of the coins and notes on 1 January 2002 and the replacement of all national currencies, the euro then began steadily appreciating, and soon regained parity with the U.S. dollar, on 15 July 2002. Since December 2002, the euro has not again fallen below parity with the U.S. dollar but instead began an ascendency. On 23 May 2003, the euro surpassed its initial ($1.18) trading value for the first time. At the end of 2004, it reached $1.3668 (€0.7316/$) as the U.S. dollar fell against all major currencies. Against the U.S. dollar, the euro temporarily weakened in 2005, falling to $1.18 (€0.85/$) in July 2005, and was stable throughout the third quarter of 2005. In November 2005 the euro again began to rise steadily against the U.S. dollar, hitting one record high after another. On 15 July 2008, the euro rose to an all-time high of $1.5990 (€0.6254/$). In a reversal, in August 2008 the euro began to drop against the U.S. dollar. In just two weeks the euro fell from its peak to $1.48 and by late October it reached a two and a half year low below $1.25.[35] On 29 December 2008, the pound sterling fell to an all-time low of £0.97855 (€1.0219/£) against the euro

The leu ([lew], plural: lei [lej]; ISO 4217 code RON; numeric code 946) is the currency of Romania. It is subdivided into 100 bani (singular: ban). On 1 July 2005, Romania underwent a currency reform, switching from the previous leu (ROL) to a new leu (RON). 1 RON is equal to 10,000 ROL.

Romania joined the European Union on 1 January 2007 and it is expected to adopt the euro in 2014.

On August 15, 1947, a revaluation took place, with a new leu replacing the old one at a rate of 20,000 old lei = 1 new leu. This revaluation, called a monetary reform or stabilisation measure (mica stabilizare, marea stabilizare), was carried out by the Communist authorities with absolutely no advance warning and without the possibility to exchange more than a fixed amount of money for the new currency. This was done in order to depose the former middle and upper classes of their last assets, after nationalization, to prepare for collectivization and to finalize the installation of communism. At the time of its introduction, 150 new lei equalled 1 U.S. dollar.

In the 1990s, after the downfall of communism, inflation ran high due to reform failures, the legalization of owning foreign currency in 1990, and the bankrupt policies of the former communist era, reaching rates as high as 300% per year in 1993. By September 2003, one euro was exchanged for more than 40,000 lei, this being its peak value. Following a number of successful monetary policies in the late 1990s and early 2000s, the situation became gradually more stable, with one digit inflation in 2005.

The Romanian leu briefly held the dubious distinction of being the world's least valued currency unit, from January (when the Turkish lira dropped six zeros) to July 2005. However, the 1,000,000 lei bill was not the highest Romanian denomination ever. This distinction belongs to the 5 million lei bill from 1947.

On 1 July 2005, the leu was revalued at the rate of 10,000 "old" lei (ROL) for one "new" leu (RON), thus psychologically bringing the purchasing power of the leu back in line with those of other major Western currencies. The term chosen for the action was "denominare", similar to the English "denomination", to signify not a conversion, but rather a total reinvention.

The first day brought difficulties adjusting to the new paper currencies and closed ATMs (that needed reprogramming) and forcing a new calculation habit that slowed down shops and annoyed some salespeople and shoppers. The old ROL currency banknotes remained in circulation until December 31, 2006 (coins remained in circulation only until December 31, 2005), but all accounts have been converted starting July 1, 2005. There is no conversion time limit between the currencies. Retailers had to display prices in both old and new currency from March 1, 2005 until June 30, 2006. The appreciation of the leu during 2005 was about 20% against a basket of major currencies.

As of 2006, the revaluation is a potential source of confusion, especially to visitors, since both old and new currency values are commonly quoted. When written, the very large amounts in old currency are usually obvious, but in speaking inhabitants might refer to an amount of 5 new lei as simply "fifty" in reference to its value 50,000 old lei.

In 1952, coins were introduced in denominations of 1, 3, 5, 10 and 25 bani, with the 1, 3 and 5 struck in aluminium bronze and the others in cupro-nickel. In 1955, cupro-nickel 50 bani were added.

In 1960, a new coinage was introduced, consisting of 15 and 25 bani, with 5 bani, 1 and 3 lei coins added in 1963. All were struck in nickel-clad steel. In 1975, aluminium replaced steel in the 5 and 15 bani, with the same change happening for the 25 bani in 1982. Aluminium 5 lei were introduced in 1978.

Following the end of the communist regime, a new coinage was introduced between 1990 and 1992, consisting of 1 leu in bronze clad steel, 5 and 10 lei in nickel plated steel, 20 and 50 lei in brass clad steel and nickel plated steel 100 lei.

As inflation took its toll, 500, 1000 and 5000 lei coins were introduced in 1999, 2000 and 2001, respectively, and were the only coins circulating when the revaluation occurred. They were all criticized for being clumsy and difficult to use. The 500 lei coins were very thick (about 0.3 cm). Despite their small value, it took only a handful of such coins to fill one's pocket. They were also made of poor material and could be occasionally found with bite marks. The 1000 lei coin was considered too small and was also cheaply made, and the 5000 lei coin was not circular (it was a dodecagon). This made it awkward to handle and difficult to use in slot machines, where it was frequently the only coin accepted. The 500, 1000 and 5000 lei coins became worth 5, 10 and 50 bani with the revaluation.

In 1952, the Ministry of Finance introduced notes for 1, 3 and 5 lei, and the Banca Republicii Populare Romane introduced 10, 25 and 100 lei notes. In 1966, the Banca Nationala a Republicii Socialiste Romania took over the production of all paper money, issuing notes for 1, 3, 5, 10, 25, 50 and 100 lei.

In 1991, 500 and 1000 lei notes were introduced, followed by 200 and 5000 lei notes in 1992, 10,000 lei in 1994, 50,000 lei in 1996, 100,000 lei in 1998, 500,000 lei in 2000 and 1 million lei in 2003. There was also a 2000 lei note, introduced in 1999; it celebrated the total solar eclipse that occurred on August 11th, 1999. The final issues of the 2000, 10,000, 50,000, 100,000, 500,000 and 1 million lei were polymer notes.

Notes in circulation at the revaluation were:

* 10,000 lei (became 1 leu)
* 50,000 lei (became 5 lei)
* 100,000 lei (became 10 lei)
* 500,000 lei (became 50 lei)
* 1,000,000 lei (became 100 lei)

In 2005, polymer notes were introduced for 1, 5, 10, 50, 100 and 500 lei. 200 lei notes were added in 2006. The designs of the 1, 5, 10, 50 and 100 lei notes are based on those of the earlier 10,000, 50,000, 100,000, 500,000 and 1 million lei notes which they replaced. The 10 lei bill was redesigned in November 2008 (most of the graphic elements are identical, some of the safety elements were withdrawn, making its safety degree similar the the lower values of 1 leu and 5 lei bills).