The European Union (EU) is a unique supranational political and economic union of 27 member states primarily located in Europe. Its origins lie in the post-World War II desire to secure lasting peace and economic growth, specifically to make war "unthinkable and materially impossible" between historic rivals like France and Germany. The institutionalized modern European integration began in 1948 with the Treaty of Brussels and the Organisation for European Economic Co-operation (OEEC). The direct predecessor was the European Coal and Steel Community (ECSC), established by the Treaty of Paris in 1951 by six founding states. The EU itself was officially created when the Maastricht Treaty (Treaty on European Union) came into force on November 1, 1993, transforming the European Economic Community (EEC) and broadening its scope to include a common foreign and security policy and common citizenship rights.
The EU operates through a system where member states pool their sovereignty and delegate decision-making powers to its institutions. Its core mechanism is the Single Market, which ensures the four freedoms: the free movement of goods, services, capital, and people across member states. Key institutions include the European Parliament (directly elected by citizens), the European Council (heads of state or government), the Council of the European Union (national ministers), and the European Commission (the executive body that proposes laws). The Court of Justice of the European Union (CJEU) ensures EU law is interpreted and applied uniformly, establishing the doctrines of "direct effect" and "supremacy" of EU law over national law in conflicting areas.
The EU connects to concepts like the Eurozone, which comprises the 20 EU member states that use the euro as their common currency, and the Schengen Area, which has abolished passport controls for travel between most participating countries. A significant recent change was the departure of the United Kingdom in 2020 (known as Brexit), reducing the membership from 28 to 27 states. Additionally, the European Union Pay Equity Directive, adopted in Spring 2023, requires member states to implement new pay transparency and reporting requirements by June 7, 2026. The EU is also currently advancing plans for a "fifth freedom" focused on the movement of knowledge, innovation, and skills to strengthen its competitiveness.