European Union (EU),international organizationcomprising 27 European countries and governing common economic, social, and security policies. Originally confined to westernEurope, the EU undertook arobust expansion into central and eastern Europe in the early 21st century. The EU’s members areAustria,Belgium,Bulgaria,Croatia,Cyprus, theCzech Republic,Denmark,Estonia,Finland,France,Germany,Greece,Hungary,Ireland,Italy,Latvia,Lithuania,Luxembourg,Malta,the Netherlands,Poland,Portugal,Romania,Slovakia,Slovenia,Spain, andSweden. TheUnited Kingdom, which had been a founding member of the EU,left the organization in 2020.

The EU was created by theMaastricht Treaty, which entered into force on November 1, 1993. The treaty was designed toenhance European political andeconomic integration by creating a singlecurrency (theeuro), a unified foreign and security policy, and common citizenship rights and by advancing cooperation in the areas of immigration, asylum, and judicial affairs. The EU was awarded theNobel Prize for Peace in 2012, in recognition of the organization’s efforts to promote peace anddemocracy in Europe.

Origins

The EU represents one in a series of efforts tointegrate Europe sinceWorld War II. At the end of the war, several western European countries sought closer economic, social, and political ties to achieveeconomic growth and military security and to promote a lasting reconciliation between France and Germany. To this end, in 1951 the leaders of six countries—Belgium, France, Italy, Luxembourg, the Netherlands, and West Germany—signed theTreaty of Paris, thereby, when it took effect in 1952, founding theEuropean Coal and Steel Community (ECSC). (The United Kingdom had been invited to join the ECSC and in 1955 sent a representative to observe discussions about its ongoing development, but the Labour government ofClement Attlee declined membership, owing perhaps to a variety of factors, including the illness of key ministers, a desire to maintain economic independence, and a failure to grasp the community’s impending significance.) The ECSC created a free-trade area for several key economic and military resources: coal, coke, steel, scrap, and iron ore. To manage the ECSC, the treaty established several supranational institutions: a High Authority to administrate, a Council of Ministers to legislate, aCommon Assembly to formulate policy, and a Court ofJustice to interpret the treaty and to resolve related disputes. A series of further international treaties and treaty revisions based largely on this model led eventually to the creation of the EU.