Enlargement of the European Union

The continental territories of the member states of the European Union (European Communities pre-1993), animated in order of accession.

Enlargement of the European Union is the process of expanding the European Union (EU) through the accession of new member states. This process began with the Inner Six, who founded the European Coal and Steel Community (the EU's predecessor) in 1952. Since then, the EU's membership has grown to twenty-seven with the most recent expansion to Bulgaria and Romania in 2007.

Currently, accession negotiations are under way with several states. The process of enlargement is sometimes referred to as European integration. However, this term is also used to refer to the intensification of co-operation between EU member states as national governments allow for the gradual harmonisation of national laws.

To join the European Union, a state needs to fulfil economic and political conditions called the Copenhagen criteria (after the Copenhagen summit in June 1993), which require a stable democratic government that respects the rule of law, and its corresponding freedoms and institutions. According to the Maastricht Treaty, each current member state and the European Parliament must agree to any enlargement.