The evolution of what is today the European Union (EU) from a regional economic agreement among six neighboring states in 1951 to today's hybrid intergovernmental and supranational organization of 28 countries across the European continent stands as an unprecedented phenomenon in the annals of history. Dynastic unions for territorial consolidation were long the norm in Europe; on a few occasions even country-level unions were arranged - the Polish-Lithuanian Commonwealth and the Austro-Hungarian Empire were examples. But for such a large number of nation-states to cede some of their sovereignty to an overarching entity is unique.

Although the EU is not a federation in the strict sense, it is far more than a free-trade association such as ASEAN, NAFTA, or Mercosur, and it has certain attributes associated with independent nations: its own flag, currency (for some members), and law-making abilities, as well as diplomatic representation and a common foreign and security policy in its dealings with external partners.

Thus, inclusion of basic intelligence on the EU has been deemed appropriate as a separate entity in The World Factbook. However, because of the EU's special status, this description is placed after the regular country entries.

Following the two devastating World Wars in the first half of the 20th century, a number of far-sighted European leaders in the late 1940s sought a response to the overwhelming desire for peace and reconciliation on the continent. In 1950, the French Foreign Minister Robert SCHUMAN proposed pooling the production of coal and steel in Western Europe and setting up an organization for that purpose that would bring France and the Federal Republic of Germany together and would be open to other countries as well. The following year, the European Coal and Steel Community (ECSC) was set up when six members - Belgium, France, West Germany, Italy, Luxembourg, and the Netherlands - signed the Treaty of Paris.

The ECSC was so successful that within a few years the decision was made to integrate other elements of the countries' economies. In 1957, envisioning an "ever closer union," the Treaties of Rome created the European Economic Community (EEC) and the European Atomic Energy Community (Euratom), and the six member states undertook to eliminate trade barriers among themselves by forming a common market. In 1967, the institutions of all three communities were formally merged into the European Community (EC), creating a single Commission, a single Council of Ministers, and the body known today as the European Parliament. Members of the European Parliament were initially selected by national parliaments, but in 1979 the first direct elections were undertaken and have been held every five years since.

In 1973, the first enlargement of the EC took place with the addition of Denmark, Ireland, and the UK. The 1980s saw further membership expansion with Greece joining in 1981 and Spain and Portugal in 1986. The 1992 Treaty of Maastricht laid the basis for further forms of cooperation in foreign and defense policy, in judicial and internal affairs, and in the creation of an economic and monetary union - including a common currency. This further integration created the European Union (EU), at the time standing alongside the EC. In 1995, Austria, Finland, and Sweden joined the EU/EC, raising the membership total to 15.

A new currency, the euro, was launched in world money markets on 1 January 1999; it became the unit of exchange for all EU member states except Denmark, Sweden, and the UK. In 2002, citizens of those 12 countries began using euro banknotes and coins. Ten new countries joined the EU in 2004 - Cyprus, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia, and Slovenia. Bulgaria and Romania joined in 2007 and Croatia in 2013, bringing the current membership to 28. (Seven of these new countries - Cyprus, Estonia, Latvia, Lithuania, Malta, Slovakia, and Slovenia - have now adopted the euro, bringing total euro-zone membership to 19.)

In an effort to ensure that the EU could function efficiently with an expanded membership, the Treaty of Nice (concluded in 2000; entered into force in 2003) set forth rules to streamline the size and procedures of EU institutions. An effort to establish a "Constitution for Europe," growing out of a Convention held in 2002-2003, foundered when it was rejected in referenda in France and the Netherlands in 2005. A subsequent effort in 2007 incorporated many of the features of the rejected draft Constitutional Treaty while also making a number of substantive and symbolic changes. The new treaty, referred to as the Treaty of Lisbon, sought to amend existing treaties rather than replace them. The treaty was approved at the EU intergovernmental conference of the then 27 member states held in Lisbon in December 2007, after which the process of national ratifications began. In October 2009, an Irish referendum approved the Lisbon Treaty (overturning a previous rejection) and cleared the way for an ultimate unanimous endorsement. Poland and the Czech Republic ratified soon after. The Lisbon Treaty came into force on 1 December 2009 and the EU officially replaced and succeeded the EC. The Treaty's provisions are part of the basic consolidated versions of the Treaty on European Union (TEU) and the Treaty on the Functioning of the European Union (TFEU) now governing what remains a very specific integration project.

UK citizens on 23 June 2016 narrowly voted to leave the EU. The EU and UK have negotiated, but not ratified, a Withdrawal Agreement that if ratified would include a status quo transition period through December 2020, which could be extended if both sides agree.

28 countries: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czechia, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, UK; note - candidate countries: Albania, Montenegro, North Macedonia, Serbia, Turkey

there are 25 overseas countries and territories (OCTs) (1 with Denmark [Greenland], 6 with France [French Polynesia; French Southern and Antarctic Lands; New Caledonia; Saint Barthelemy; Saint Pierre and Miquelon; Wallis and Futuna], 6 with the Netherlands [Aruba, Bonaire, Curacao, Saba, Sint Eustatius, Sint Maarten], and 12 with the UK [Anguilla; Bermuda; British Antarctic Territory; British Indian Ocean Territory; British Virgin Islands; Cayman Islands; Falkland Islands; Montserrat; Pitcairn Islands; Saint Helena, Ascension, and Tristan da Cunha; South Georgia and the South Sandwich Islands; Turks and Caicos Islands]), of which 22 have joined the Overseas Countries and Territories Association (OCTA); the 3 OCTs that are not part of OCTA (British Antarctic Territory, British Indian Ocean Territory, South Georgia and the South Sandwich Islands) do not have a permanent population

under the EU treaties there are three distinct institutions, each of which conducts functions that may be regarded as executive in nature:
European Council - brings together heads of state and government, along with the president of the European Commission, and meets at least four times a year; its aim is to provide the impetus for the development of the Union and to issue general policy guidelines; the Treaty of Lisbon established the position of "permanent" (full-time) president of the European Council; leaders of the EU member states appoint the president for a 2 1/2 year term, renewable once; the president's responsibilities include chairing the EU summits and providing policy and organizational continuity; the current president is Donald TUSK (Poland), since 1 December 2014, succeeding Herman VAN ROMPUY (Belgian; 2009-14)
Council of the European Commission - consists of ministers of each EU member state and meets regularly in 10 different configurations depending on the subject matter; it conducts policymaking and coordinating functions as well as legislative functions; ministers of EU member states chair meetings of the Council of the EU based on a 6-month rotating presidency except for the meetings of EU Foreign Ministers in the Foreign Affairs Council that are chaired by the High Representative for Foreign Affairs and Security Policy
European Commission - headed by a College of Commissioners comprised of 28 members (one from each member country) including the president; each commissioner is responsible for one or more policy areas; the Commission's main responsibilities include the sole right to initiate EU legislation (except for foreign and security/defense policy), promoting the general interest of the EU, acting as "guardian of the Treaties" by monitoring the application of EU law, implementing/executing the EU budget, managing programs, negotiating on the EU's behalf in core policy areas such as trade, and ensuring the Union's external representation in some policy areas; its current president is Jean-Claude JUNCKER (Luxembourg) elected on 15 July 2014 (took office on 1 November 2014); the president of the European Commission is nominated by the European Council and formally "elected" by the European Parliament; the Commission president allocates specific responsibilities among the members of the College (appointed by common accord of the member state governments in consultation with the president-elect); the European Parliament confirms the entire Commission for a 5-year term; President JUNCKER reorganized the structure of the College around clusters or project teams coordinated by 7 vice presidents in line with the current Commission's main political priorities and appointed Frans TIMMERMANS (Netherlands) to act as his first vice president; the confirmation process for the next Commission expected be held in the fall of 2019

The 28 member states that make up the EU have adopted an internal single market with free movement of goods, services, capital, and labor. The EU, which is also a customs union, aims to bolster Europe's trade position and its political and economic weight in international affairs.

Despite great differences in per capita income among member states (from $28,000 to $109,000) and in national attitudes toward issues like inflation, debt, and foreign trade, the EU has achieved a high degree of coordination of monetary and fiscal policies. A common currency – the euro – circulates among 19 of the member states that make up the European Economic and Monetary Union (EMU). Eleven member states introduced the euro as their common currency on 1 January 1999 (Greece did so two years later). Since 2004, 13 states acceded to the EU. Of the 13, Slovenia (2007), Cyprus and Malta (2008), Slovakia (2009), Estonia (2011), Latvia (2014), and Lithuania (2015) have adopted the euro; 7 other member states - excluding the UK and Denmark, which have formal opt-outs - are required by EU treaties to adopt the common currency upon meeting fiscal and monetary convergence criteria.

The EU economy posted moderate GDP growth for 2014 through 2017, capping five years of sustained growth since the 2008-09 global economic crisis and the ensuing sovereign debt crisis in the euro zone in 2011. However, the bloc’s recovery has been uneven. Some EU member states (Czechia, Ireland, Malta, Romania, Sweden, and Spain) have recorded strong growth, others (Italy and the UK) are experiencing modest expansion and some (Greece) have only recently shaken off recession. Only Greece remains under an EU rescue program (due to end in August 2018), while Cyprus, Ireland, Portugal, and Spain have successfully concluded their agreements. Overall, the EU’s recovery has been buoyed by lower commodities prices and accommodative monetary policy, which has lowered interest rates and stimulated demand. The euro zone, which makes up about 70% of the total EU economy, is also performing well, achieving a growth rate not seen in a decade. In October 2017 the European Central Bank (ECB) announced it would extend its bond-buying program through September 2018, and possibly beyond that date, to keep the euro zone recovery on track. The ECB’s efforts to spur more lending and investment through its asset-buying program, negative interest rates, and long-term loan refinancing programs have not yet raised inflation in line with the ECB’s statutory target of just under 2%.

Despite its performance, high unemployment in some member states, high levels of public and private debt, muted productivity, an incomplete single market in services, and an aging population remain sources of potential drag on the EU’s future growth. Moreover, the EU economy remains vulnerable to a slowdown of global trade and bouts of political and financial turmoil. In June 2016, the UK voted to withdraw from the EU, the first member country ever to attempt to secede. Continued uncertainty about the implications of the UK’s exit from the EU (set for March 2019) could hurt consumer and investor confidence and dampen EU growth, particularly if trade and cross-border investment significantly declines. Political disagreements between EU member states on reforms to fiscal and economic policy also may impair the EU’s ability to bolster its crisis-prevention and resolution mechanisms. International investors’ fears of a broad dissolution of the single currency area have largely dissipated, but these concerns could resurface if elected leaders implement policies that contravene euro-zone budget or banking rules. State interventions in ailing banks, including rescue of banks in Italy and resolution of banks in Spain, have eased financial vulnerabilities in the European banking sector even though some banks are struggling with low profitability and a large stock of bad loans, fragilities that could precipitate localized crises. Externally, the EU has continued to pursue comprehensive free trade agreements to expand EU external market share, particularly with Asian countries; EU and Japanese leaders reached a political-level agreement on a free trade agreement in July 2017, and agreement with Mexico in April 2018 on updates to an existing free trade agreement.

as a political union, the EU has no border disputes with neighboring countries, but Estonia has no land boundary agreements with Russia, Slovenia disputes its land and maritime boundaries with Croatia, and Spain has territorial and maritime disputes with Morocco and with the UK over Gibraltar; the EU has set up a Schengen area - consisting of 22 EU member states that have signed the convention implementing the Schengen agreements or "acquis" (1985 and 1990) on the free movement of persons and the harmonization of border controls in Europe; these agreements became incorporated into EU law with the implementation of the 1997 Treaty of Amsterdam on 1 May 1999; in addition, non-EU states Iceland and Norway (as part of the Nordic Union) have been included in the Schengen area since 1996 (full members in 2001), Switzerland since 2008, and Liechtenstein since 2011 bringing the total current membership to 26; the UK (since 2000) and Ireland (since 2002) take part in only some aspects of the Schengen area, especially with respect to police and criminal matters; nine of the 13 new member states that joined the EU since 2004 joined Schengen on 21 December 2007; of the four remaining EU states, Romania, Bulgaria, and Croatia are obligated to eventually join, while Cyprus' entry is held up by the ongoing Cyprus dispute