The European Union (EU) currently has 27 Member States. Following the first six Member States — Belgium, France, Germany, Italy, Luxembourg and the Netherlands — 21 countries have acceded to the Union:
- 1973: Denmark, Ireland and the United Kingdom;
- 1981: Greece;
- 1986: Spain and Portugal;
- 1995: Austria, Finland and Sweden;
- 2004: Cyprus, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia;
- 2007: Bulgaria and Romania.
Croatia, the Former Yugoslav Republic of Macedonia and Turkey have the status of candidate countries. Accession negotiations with Croatia and Turkey opened on 3 October 2005.
The countries of the Western Balkans which are engaged in the stabilisation and association process have the status of potential candidate countries. These are Albania, Bosnia-Herzegovina, Montenegro and Serbia, including Kosovo, as defined by UN Security Council Resolution 1244.
Iceland submitted an application for accession to the EU in July 2009. The country, which is a member of the European Economic Area and the Schengen area, has already reached a high level of integration with the EU. The Council shall decide on the opening of accession negotiations.