The European Union (EU) is an economic and political union of 27 member states that are located primarily in Europe. The EU operates through a system of supranational independent institutions and intergovernmental negotiated decisions by the member states. Institutions of the EU include the European Commission, the Council of the European Union, the European Council, the Court of Justice of the European Union, the European Central Bank, the Court of Auditors, and the European Parliament. The European Parliament is elected every five years by EU citizens. The EU's de facto capital is Brussels.

The EU traces its origins from the European Coal and Steel Community (ECSC) and the European Economic Community (EEC), formed by the Inner Six countries in 1951 and 1958 respectively. In the intervening years the community and its successors have grown in size by the accession of new member states and in power by the addition of policy areas to its remit. The Maastricht Treaty established the European Union under its current name in 1993. The latest major amendment to the constitutional basis of the EU, the Treaty of Lisbon, came into force in 2009.