The European Union (EU) is a political and economic union of 27 member states located primarily in Europe. It is a supranational union with a total area of 4,233,255 km2 and an estimated population of just under 452 million as of 2026. Its member states generated a nominal gross domestic product of around €18.802 trillion in 2025, accounting for approximately one sixth of global economic output. The EU is often described as a sui generis political entity combining characteristics of both a federation and a confederation.
The EU’s cornerstone, the Customs Union, paved the way to establishing an internal single market based on a standardised legal framework and legislation that apply in all member states in those matters, and only those matters, where the states have agreed to act as one. EU policies aim to ensure the free movement of people, goods, services and capital within the internal market; enact legislation in justice and home affairs; and maintain common policies on trade, agriculture, fisheries, and regional development.
Membership and enlargement
To join the EU, a state needs to fulfil economic and political conditions called the Copenhagen criteria, 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.
The EU’s predecessor, the European Economic Community, was founded with the Inner Six member states in 1958, when the Treaty of Rome came into force. Since then, the EU’s membership has grown to twenty-seven, with the latest member state being Croatia, which joined in July 2013. As of 2026, there are nine current EU candidate countries: Albania, Bosnia and Herzegovina, Georgia, Moldova, Montenegro, North Macedonia, Serbia, Turkey, and Ukraine. Among the six candidates with open negotiations, the most advanced stage of negotiations has so far been reached by Montenegro and Albania.
Governance
Member states have agreed by the treaties to share their own sovereignty through the institutions of the European Union in certain aspects of government. State governments must agree unanimously in the Council for the union to adopt some policies; for others, collective decisions are made by qualified majority voting. A founding principle of the union is subsidiarity, meaning that decisions are taken collectively if and only if they cannot realistically be taken individually. Each member country appoints to the European Commission a European commissioner; the commissioners do not represent their member state, but instead work collectively in the interests of all.