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 best known of these is ISO 3166-1. The term country code frequently refers to international dialing codes, the E.164 country calling codes.
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, for example,
- 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 
- 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
- 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
- FIFA (Fédération Internationale de Football Association) assigns a three-letter code (dubbed FIFA Trigramme) to each of its member and non-member countries: List of FIFA country codes
- Federal Information Processing Standard (FIPS) 10-4 defined two-letter codes used by the U.S. government and in the CIA World Factbook: list of FIPS country codes. On September 2, 2008, FIPS 10-4 was one of ten standards withdrawn by NIST as a Federal Information Processing Standard.
- GOST 7.67: country codes in Cyrillic from the GOST standards committee
- From the International Civil Aviation Organization (ICAO):
- International Olympic Committee (IOC) three-letter codes used in sporting events: list of IOC country codes
- From the International Telecommunication Union (ITU):
- the E.164 international telephone dialing 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, and so on) define the country: the ITU prefix,
- ITU letter codes for member-countries,
- ITU prefix - amateur and experimental stations - The International Telecommunications Union (ITU) assigns national telecommuncation prefixes for amateur and experimental radio use, so that operators can be identified by their country of origin. These prefixes are legally administered by the national entity to which prefix ranges are assigned.
- Three-digit codes used to identify countries in maritime mobile radio transmissions, known as maritime identification digits
- License plates for automobiles:
- North Atlantic Treaty Organisation (NATO) used two-letter codes of its own: list of NATO country codes. They were largely borrowed from the FIPS 10-4 codes mentioned below. In 2003 the eighth edition of the Standardisation Agreement (STANAG) adopted the ISO 3166 three-letter codes with one exception (the code for Macedonia). With the ninth edition, NATO is transitioning to four- and six-letter codes based on ISO 3166 with a few exceptions and additions
- United Nations Development Programme (UNDP) also has its own list of trigram country codes
- World Intellectual Property Organization (WIPO): WIPO ST.3 gives two-letter codes to countries and regional intellectual property organizations
- World Meteorological Organization (WMO) has its own list of country codes, used in reporting meteorological observations
- UIC (the International Union of Railways: UIC Country Codes
The developers of ISO 3166 intended that in time it would replace other coding systems in existence.
Other codings 
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 GS1 Company Prefixes used to identify products, for example, in barcodes, designate (national) numbering agencies.
Lists of country codes by country 
See also 
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- Federal Register, September 2, 2008 (Volume 73, Number 170), page 51276
- Comparison of various systems
- Another comparison: Country Codes at statoids.com
- A comparison with ISO, IFS and others with notes
- United Nations Region Codes
- Country codes with city codes inside each country with short country description