The European Union (EU) is a political and economic union of 27 member states that are located primarily in Europe. The union has a total area of 4,233,255.3 km2 (1,634,469.0 sq mi) and an estimated total population of about 447 million. An internal single market has been established through a standardised system of laws 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. Passport controls have been abolished for travel within the Schengen Area. The eurozone is a monetary union established in 1999, coming into full force in 2002, that is composed of the 19 EU member states that use the euro currency. The EU has often been described as a sui generis political entity (without precedent or comparison) with the characteristics of either a federation or confederation.The union and EU citizenship were established when the Maastricht Treaty came into force in 1993. The EU traces its origins to the European Coal and Steel Community (ECSC) and the European Economic Community (EEC), established, respectively, by the 1951 Treaty of Paris and 1957 Treaty of Rome. The original member states of what came to be known as the European Communities were the Inner Six: Belgium, France, Italy, Luxembourg, the Netherlands, and West Germany. The communities and their successors have grown in size by the accession of 21 new member states and in power by the addition of policy areas to their remit. The latest major amendment to the constitutional basis of the EU, the Treaty of Lisbon, came into force in 2009. In 2020, the United Kingdom became the only member state to leave the EU. Before this, four territories of current member states had left the EU or its forerunners. There are several other countries that are negotiating to join the European Union.

Containing some 5.8 percent of the world population in 2020, the EU had generated a nominal gross domestic product (GDP) of around US$17.1 trillion in 2021, constituting approximately 18 percent of global nominal GDP. Additionally, all EU countries have a very high Human Development Index according to the United Nations Development Programme. In 2012, the EU was awarded the Nobel Peace Prize. Through the Common Foreign and Security Policy, the union has developed a role in external relations and defence. It maintains permanent diplomatic missions throughout the world and represents itself at the United Nations, the World Trade Organization, the G7 and the G20. Due to its global influence, the European Union has been described by some scholars as an emerging superpower.