European Union


Enlargement is the process whereby countries join the EU. Since it was founded in 1957, the EU has grown from 6 countries to 28.

Spreading prosperity and democracy

Over the past 50 years, widening EU membership has promoted economic growth and strengthened democratic forces in countries emerging from dictatorship.

Uniting East and West

The 6 founding members of the EU in 1957 were Belgium, France, Germany, Italy, Luxembourg and the Netherlands.

Several other West European countries joined after 1973.

Following the collapse of their regimes in 1989, many former communist countries from central and eastern Europe became EU members in 2 waves, between 2004 and 2007. In 2013, Croatia became the 28th country to join.

Full list of countries with year of joining

Who can join?

The Treaty on European Union states that any European country may apply for membership if it respects the EU's democratic values and is committed to promoting them.

But specifically, a country can only join if it meets all the membership criteria:

  • political – it must have stable institutions guaranteeing democracy, the rule of law and human rights
  • economic – it must have a functioning market economy and be able to cope with competitive pressure and market forces within the EU
  • legal – it must accept established EU law and practice – especially the major goals of political, economic and monetary union.

How does it work?

The process has 3 stages (all subject to approval by all existing EU countries):

  1. a country is offered the prospect of membership
  2. the country becomes an official candidate for membership
  3. the candidate moves on to formal membership negotiations, a process that usually involves reforms to adopt established EU law.

When the negotiations and accompanying reforms have been completed to the satisfaction of both sides, the country can join the EU – again, if all existing EU countries agree.

Which countries might join next?

See the list of candidate countries and potential candidates


Manuscript updated in June 2015

This publication is part of the 'European Union explained' series

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