The European Union (EU) is a supranational political and economic union of 27 member states located primarily in Europe.Member states are party to the EU's founding treaties and have agreed to share aspects of their sovereignty through common institutions, with some decisions requiring unanimous agreement among governments and others made by qualified majority voting. The EU operates a single market with free movement of goods, capital, services, and people, a common external trade policy, and for most members a common currency, the euro. The nature and proper extent of the union - whether it should function primarily as an economic and regulatory body or develop further political, military, and fiscal integration - is itself contested; see european-union-nature-and-purpose-debate.

A founding principle of the union is subsidiarity, meaning decisions are taken collectively only when they cannot realistically be taken at the national, regional, or local level. The EU's main institutions include the European Commission, which proposes legislation and enforces EU law; the European Parliament, whose members are directly elected by EU citizens; and the Council of the European Union, which represents the governments of member states. Since the 2024 European elections there are 720 Members of the European Parliament for the 2024-2029 legislative term. The presidency of the Council rotates among member states every six months.

Twenty of the 27 member states use the euro as their currency, while Denmark holds a permanent opt-out and Sweden, Poland, Czechia, Hungary, Romania, and Bulgaria continue to use their own national currencies. Bulgaria is scheduled to join the euro area in January 2026. Most EU members also participate in the Schengen Area, a separate zone of 29 European states that have abolished passport checks at shared internal borders, though Ireland has an opt-out from Schengen and Cyprus has not yet fully joined it, while non-EU states Norway, Iceland, Switzerland, and Liechtenstein are full Schengen members.

The EU has an active enlargement process. As of 2026, nine states hold official candidate status: Albania, Bosnia and Herzegovina, Georgia, Moldova, Montenegro, North Macedonia, Serbia, Turkey, and Ukraine, with Kosovo recognized as a potential candidate. Six candidates are engaged in active negotiations, and Montenegro and Albania have reached the most advanced stage so far attained. Accession requires unanimous consent of existing members and a candidate's fulfillment of the Copenhagen criteria. The pace and desirability of further enlargement, particularly regarding Ukraine and Turkey, is a matter of dispute among member states; see european-union-enlargement-debate.

The United Kingdom remains the only state to have withdrawn from the EU, having left on 31 January 2020 following the 2016 referendum. For the longer historical background of the union's formation and development, see European Union.

• Federalist / Pro-Integration Viewpoint - holds that deeper political, fiscal, and military integration is necessary for the EU to function effectively and project power in a multipolar world. See European Union - Federalist Viewpoint.
• Intergovernmentalist / Sovereigntist Viewpoint - holds that the EU should remain primarily a cooperative framework among sovereign nation-states, with decision-making authority retained at the national level wherever possible. See european-union-intergovernmentalist-viewpoint.
• Euroskeptic Viewpoint - holds that EU membership imposes excessive regulatory, fiscal, or migration-related costs on member states and that national parliaments have ceded too much authority to unelected supranational bodies. See european-union-euroskeptic-viewpoint.
• Strategic Autonomy Viewpoint - holds that the EU must reduce its economic and security dependence on the United States, China, and other external powers by developing independent defense, energy, and industrial capacity. See european-union-strategic-autonomy-viewpoint.
• Atlanticist Viewpoint - holds that EU security and defense policy should remain closely coordinated with NATO and the United States rather than developing parallel or competing structures. See european-union-atlanticist-viewpoint.
• Withdrawalist Viewpoint - holds that individual member states would be better served outside the EU, citing the UK's departure as a precedent worth following or avoiding. See european-union-withdrawalist-viewpoint.

• Disputes over the rule of law and judicial independence in Hungary and Poland have led to EU sanctions mechanisms and withheld funding. See european-union-rule-of-law-hungary-poland-controversy.
• The question of whether and how quickly Ukraine should be admitted amid an ongoing war has divided member states over security guarantees and budgetary implications. See european-union-ukraine-accession-controversy.
• Migration policy, including the distribution of asylum seekers among member states, has produced sustained disagreement and legal disputes. See European Union Migration Policy - Border and Asylum System Controversy.

• History: European Union
• Debate: european-union-enlargement-debate
• Debate: european-union-nature-and-purpose-debate
• Viewpoint Debate: european-union-strategic-autonomy-viewpoint-debate
• Viewpoint Debate: european-union-atlanticist-viewpoint-debate
• Controversy: european-union-rule-of-law-hungary-poland-controversy
• Controversy: european-union-ukraine-accession-controversy
• Controversy: European Union Migration Policy - Border and Asylum System Controversy
• Related Main Topic: NATO
• Related Main Topic: brexit
• Related Main Topic: Eurozone

1. “Member state of the European Union,” Wikipedia, last modified April 28, 2026, https://en.wikipedia.org/wiki/Member_state_of_the_European_Union.
2. “Potential enlargement of the European Union,” Wikipedia, last modified June 2026, https://en.wikipedia.org/wiki/Potential_enlargement_of_the_European_Union.
3. “EU countries,” European Union, accessed June 26, 2026, https://european-union.europa.eu/principles-countries-history/eu-countries_en.