European Union (EU) is a legal political community, established for the European integration and common governance of the citizens and states of Europe. It consists of 28 European states, and was established by the entry into force of the Treaty on European Union on 1 November 1993.
Member States
| Country | Code | Date of registration | Currency |
 Austria | AT | 1995 | Euro (since 2002) |
 Belgium | BE | 1957 (founding country) | Euro (since 2002) |
 Great Britain | GB | 1973 (planned resignation in 2019) | British pound |
 Bulgaria | BG | 2007 | Bulgarian levo |
 Czech Republic | CZ | 2004 | Czech crown |
 Denmark | DK | 1973 | Danish crown |
 Estonia | EE | 2004 | Euro (since 2011) |
 Finland | FI | 1995 | Euro (since 2002) |
 France | FR | 1957 (founding country) | Euro (since 2002) |
 Germany | DE | 1957 (founding country) | Euro (since 2002) |
 Greece | GR | 1981 | Euro (since 2002) |
 Spain | ES | 1986 | Euro (since 2002) |
 Hungary | HU | 2004 | Hungarian forinto |
 Ireland | IE | 1973 | Euro (since 2002) |
 Italy | IT | 1957 (founding country) | Euro (since 2002) |
 Cyprus | CY | 2004 | Euro (since 2008) |
 Croatia | HR | 2013 | Croatian kunao |
 Latvia | LV | 2004 | Latvian lat, Euro (since 2014) |
 Lithuania | LT | 2004 | Lithuanian lido |
 Luxembourg | LU | 1957 (founding country) | Euro (since 2002) |
 Malta | MT | 2004 | Euro (since 2008) |
 The Netherlands | NL | 1957 (founding country) | Euro (since 2002) |
 Poland | PL | 2004 | Pola zloto |
 Portugal | PT | 1986 | Euro (since 2002) |
 Romania | RO | 2007 | Romanian lei |
 Slovakia | SK | 2004 | Euro (since 2009) |
 Slovenia | SI | 2004 | Euro (since 2007) |
 Sweden | SE | 1995 | Swedish krona |
Candidates
Until 2025 there are supposed registrations of Serbian and Montenegro.
Another 3 countries are candidates: Northern Macedonia, Albania and Turkey. While Macedonia and Albania are relatively well on track and their acceptance is expected in 2020; Turkey is politically disputed and due to the current political atmosphere in Turkey there is a frozen accession negotiation.
Considered (but meanwhile not fully official candidates) are also Armenia, Azerbaijan, Bosnia and Herzegovina, Georgia, Kosovo (with disputed status), Kazakhstan, Iceland, Moldova, Norway, San Marino, Switzerland, Ukraine. Eventually could join as well Belarus, and Russia.
A specific question is about the states Andorra, Liechtenstein, Monaco, San Marino and Vatican. The Vatican does not meet the membership requirement for demoralism and can join. Benefit for other countries is doubtful, because they have good contracts with the European Union anyway. In addition, the bureaucracy of the European Union is not well adapted to small states.