The European Union or EU is an international organisation of 25 European states, established with that name by the Treaty on European Union (commonly known as the Maastricht treaty) in 1992 but many aspects of it existing since the 1950s. Its headquarters are in Brussels.

The European Union has many activities, the most important being a common single market, consisting of a customs union, a single currency (adopted by 12 out of 25 member states), a Common Agricultural Policy and a Common Fisheries Policy. The European Union also has various initiatives to co-ordinate activities of the member states.

The next expansion is set to take place in 2007, with Bulgaria and Romania likely to join at that date. Croatia is also an official candidate, and is likely to join within a similar timescale. Turkey is the only other official candidate, though with a less definitive estimate for an accession date. Further information about future enlargements can be found in the Enlargement of the European Union article.

The total area of the 25 member states (2004) of the European Union is 3,892,685 km². Were it a country, it would be the seventh largest in the world by area. The number of EU citizens (all EU member state citizens or subjects, under the terms of the Maastricht treaty) in the 25 member EU is approximately 453 million as of March 2004. This would be the third largest in the world after India and China.

Many countries, such as Monaco and Andorra, while not being member states have special agreements with the union.

Europe is a continent whose boundaries are generally regarded as being: the Atlantic Ocean in the west, the Arctic Ocean to the north, the Ural Mountains and Ural River (the Emba River in other definitions) in the east, the Caspian Sea, Caucasus mountains (the Kuma-Manych Depression in other definitions) and Black Sea in the southeast, and the Mediterranean Sea to the south. Together with Asia, Europe forms the supercontinent Eurasia, of which Europe is the western fifth.

In terms of area, Europe is the world's second smallest continent, with an area of 10,400,000 km² (4,000,000 square miles), making it slightly larger than Australia.

In terms of population it is the third largest continent after Asia and Africa. The population of Europe in 2001 was estimated to be 666,498,000: roughly one seventh of the world's population.

According to Homer the name Europe (Greek: Ευρώπη) was originally given to central Greece. Later it stood for mainland Greece and by 500 BC its meaning was extended to all the lands of the north.

The term Europe is often said to derive from Greek words meaning broad (eurys) and face (ops). Many, however, see a Semitic origin, pointing to the Semitic word ereb which means "sunset". From a Middle Eastern viewpoint, the sun sets over Europe: the lands to the west. In ancient mythology, Europa was a Phoenician princess who was abducted by a bull-shaped Zeus.