The enlargement process

Colour-coded map showing stages of EU enlargement
EU enlargement milestones since 1954 © DEA

Since 1957, the European Union (EU) has been continually gaining new members. In 2004, ten candidate countries joined the EU at the same time, marking the largest expansion to date, as only two to three countries had joined in a single year prior to that. The EU enlargement process is also significant because in many countries the possibility of joining the EU plays a major role in domestic politics. The UK's withdrawal from the EU in 2020 was a first, after decades of EU expansion.

In 2004, the EU welcomed ten new member states in its largest enlargement round to date: Cyprus, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia. Two additional countries – Bulgaria and Romania – joined in 2007. Since Croatia's accession on 1 July 2013, no other countries have joined the EU. Following the UK's withdrawal in 2020, the EU now has 27 member states.

Significance and consequences of EU enlargement

The prospect of joining the EU – and subsequent membership – have played a major role in new member states' transition to democracy and a social market economy. The EU's eastward enlargement helped to overcome the ideological division of Europe caused by the Cold War and represented a decisive step towards greater stability and shared prosperity for the continent. The enlargement process has also increased the EU's population and number of official languages. Irish became an official EU language in 2007. Croatia's accession in 2013 brought the number of official languages to 24. Furthermore, the Council of the EU recognises several regional languages, such as Catalan and Basque. Member states may also request translations of certain documents in these regional languages.

Who can become a candidate for EU membership?

Potential candidates for EU membership have to meet strict political, economic and legal conditions, known as the 'Copenhagen criteria'. The EU's capacity to integrate new members will be an increasingly important criterion for the future enlargement process: with a growing number of member states, the EU must ensure its continued ability to take action and make decisions, meet budgetary commitments, and implement common policies effectively.

Enlargement process: development since 2003

In 2003, the EU held out the prospect of membership to the countries of the Western Balkans, provided they met the necessary criteria. Croatia's accession proved that this was not an empty promise. The EU has begun accession negotiations with Serbia and Montenegro. Albania, Bosnia and Herzegovina, Kosovo and North Macedonia also have a clear prospect of joining. In addition to the Balkan states' membership, the possibility of Turkey joining the EU, whose accession negotiations began in 2005, is also a controversial issue within the EU. Moreover, the European Commission's most recent accession report on the situation in Turkey highlights, among other issues, serious backsliding with respect to judicial independence and freedom of expression in the country