The European Union (EU) is a unique political and economic union of 27 member states, often described as a sui generis entity that combines characteristics of a federation and a confederation. Its origins lie in the post-World War II effort to secure lasting peace and economic growth by making war "unthinkable and materially impossible." This goal was first institutionalized with the European Coal and Steel Community (ECSC), founded in 1951 by six countries following the Schuman Declaration of 9 May 1950. The EU itself was officially created by the Maastricht Treaty (Treaty on European Union) in 1992, which entered into force on 1 November 1993.
The EU operates through a set of institutions listed in Article 13 of the Treaty on the European Union (TEU), including the European Parliament (representing citizens), the Council of the European Union (representing member state governments), and the European Commission (the executive arm). The European Commission proposes new laws, which are then adopted jointly by the Parliament and the Council through the Ordinary Legislative Procedure. The Treaty of Rome (1957) established the European Economic Community (EEC), which created a single market based on the four freedoms of movement: goods, people, services, and capital, which remain integral pillars of the EU.
Related concepts include the Eurozone, which is the group of 21 EU member states that use the single currency, the euro, and the Schengen Area, a zone of 29 countries that have abolished passport controls at their mutual borders. The EU's structure and powers were last significantly updated by the Treaty of Lisbon, signed on 13 December 2007, which formally entered into force on 1 December 2009. This treaty gave the Charter of Fundamental Rights a legally binding character via Article 6(1) TEU and introduced Article 50 TEU, which provides the mechanism for a member state to withdraw. The most significant recent change was the withdrawal of the United Kingdom (Brexit) on 31 January 2020. More recent changes include the implementation of the Entry/Exit System (EES), a new digital border system that started on 12 October 2025, and the upcoming European Travel Information and Authorisation System (ETIAS), expected in Autumn 2026.