The European Currency Unit (ECU) was a basket of the currencies of the European Community member states, used as the unit of account of the European Community from 13 March 1979 until on 1 January 1999, when it was replaced by the euro.

Although the acronym ECU is formed from English words, écu is also the name of an ancient French coin, minted for the first time by Luis IX in the 12th century. That was one (perhaps the main) reason that a new name was devised for its successor currency, euro, which was felt not to favour any single language. In fact, Helmut Kohl, Germany’s Chancellor at the time said that “ECU” sounded to him like Ein Kuh, which in German means “a cow”, reason for which he wanted to change the name of the currency.

On 1 January 1999, the euro replaced the ECU, at the value €1 = 1 ECU. Unlike the ECU, the euro is a real currency, although not all member states participate. Two of the countries in the ECU basket of currencies, UK and Denmark, did not join the Eurozone, and a third, Greece, joined late. On the other hand, Finland and Austria joined the Eurozone from the beginning although their currencies were not part of the ECU basket (since they had joined the EU in 1995, two years after the ECU composition was "frozen").

Although at first the ECU was a unit of account and was used for a number of international financial transactions, it was expected to be converted into a circulating currency. In most European countries there were pattern coins issued exploring the design possibilities of the anticipated new coinage. Some of these issues were design exercises carried out by official mints, others were privately issued.

These coins were issued in Spain and became quite popular among collectors worldwide.