Country codes are short alphabetic or numeric geographical codes (geocodes) developed to represent countries and dependent areas, for use in data processing and communications. Several different systems have been developed to do this. The most famous of these is ISO 3166-1.
Lists of country codes by country
Main article: ISO 3166-1
This standard defines for most of the countries and dependent areas in the world:
- a two letter (ISO 3166-1 alpha-2)
- a three-letter (ISO 3166-1 alpha-3), and
- a three-digit numeric (ISO 3166-1 numeric) code.
The two-letter codes are used as the basis for some other codes or applications, e.g.
- for ISO 4217 currency codes and
- with deviations for country code top-level domain names (ccTLDs) on the Internet: list of Internet TLDs.
For more applications see ISO 3166-1 alpha-2.
Other country codes
- The International Olympic Committee (IOC) three letter codes used in sporting events: list of IOC country codes
- The Fédération Internationale de Football Association (FIFA) assigns a three-letter code (dubbed FIFA Trigramme) to each of its member and non-member countries: List of FIFA country codes
- The North Atlantic Treaty Organisation (NATO) used two-letter codes of its own: list of NATO country codes. In 2003, the eighth edition of the Standardisation Agreement (STANAG) adopted the ISO 3166 three-letter codes with one exception (the code for Macedonia).
- The coding system for car license plates under the 1949 and 1968 United Nations Road Traffic Conventions (distinguishing signs of vehicles in international traffic): List of international license plate codes 
- The Federal Information Processing Standard (FIPS) two letter codes used by the US government and in the CIA World Factbook: list of FIPS country codes, See also List of FIPS region codes for a set of 4-character region codes, also assigned by FIPS.
- The coding system for diplomatic license plates in the United States, assigned by the U.S. State Department.
- From the International Telecommunication Union (ITU):
- the E.164 international dialling codes: list of country calling codes with 1-3 digits,
- the E.212 mobile country codes (MCC), for mobile/wireless phone addresses,
- the first few characters of call signs of radio stations (maritime, aeronautical, amateur radio, broadcasting, etc.) define the country: the ITU prefix,
- ITU letter codes for member-countries,
- Three-digit codes used to identify countries in maritime mobile radio transmissions, known as maritime identification digits
- European Union:
- Before the 2004 EU enlargement the EU used the UN Road Traffic Conventions license plate codes; since then, it uses ISO 3166-1, with 2 exceptions: EL (not GR) is used for Greece, and UK (not GB) is used for the United Kingdom. EU Interinstitutional style guide
- The Nomenclature des unités territoriales statistiques (Nomenclature of territorial units for statistics, NUTS) of the European Union, mostly focusing on subdivisions of the EU member states
- From the International Civil Aviation Organization (ICAO):
- aircraft registration prefixes,
- nationality letters for location indicators.
The developers of ISO 3166 intended that in time it would replace other coding systems in existence.
The following can represent countries:
- The initial digits of International Standard Book Numbers (ISBN) are group identifiers for countries, areas, or language regions.
- The first three digits of EAN-UCC article numbers, e.g. in barcodes, designate (national) numbering agencies.
- Comparison of various systems: http://www.unc.edu/~rowlett/units/codes/country.htm
- Another comparison: http://www.statoids.com/wab.html
- Country calling codes
- list with flags