Map illustrating the European Union’s changing composition following the successive enlargements of the European Communities, from the six founding countries to the Union of 28 Member States. This map also shows the candidate countries currently in accession negotiations, the other candidate countries and the potential candidates.

On 1 January 1973, the accession of Denmark, Ireland and the United Kingdom brings the number of Member States of the European Community to nine.

On 1 January 1981, the accession of Greece brings the number of Member States of the European Communities to ten.

On 1 January 1995, the accession of Austria, Finland and Sweden increases the number of Member States of the European Union to 15.

On 1 May 2004, the accession of ten States brings the number of Member States in the European Union up to twenty-five.

With the accession of Bulgaria and Romania on 1 January 2007, the number of Member States of the European Union increases to 27.

With the accession of Croatia on 1 July 2013, the number of Member States of the European Union increases to 28.