Enlargement of the European Union

From six to twenty-seven (and back to twenty-seven): the EU’s membership history

The European Economic Community started life in 1957 with six members. By 2020 it had become the European Union of 27, having passed through 8 distinct enlargement waves and one withdrawal. This page traces that history from the source data the rest of the euverse trackers depend on: the small hand-curated master file listing every Member State’s accession year and (where applicable) exit year.

Data as of 2026-06-08 08:21 UTC

Member State count over time

The 2004 “Big Bang” enlargement remains the largest single accession in EU history: ten countries (most of post-Soviet Central and Eastern Europe, plus Malta and Cyprus) joined on the same day. The chart’s only dip is 2020, when the United Kingdom became the first (and so far only) Member State to leave.

Accession timeline

Member State table

Candidate countries

The chart and table above only show current and historical Member States. As of June 2026, 9 countries hold formal candidate status and 1 hold potential-candidate status. Together they describe the EU’s current enlargement pipeline.

Cite

Ovádek, M. euverse: Enlargement of the European Union. Accessed 8 June 2026. Available at https://michalovadek.github.io/euverse/trackers/eu-enlargement.html.