ISO 3166-3 is an international standard that defines codes for outdated ISO 3166-1 country codes and is part of ISO 3166.

If after 1974 countries

the codes were withdrawn from ISO 3166-1 and with addition of two letters put in ISO 3166-3.

ISO 3166-3 is four-digit-alphabetic and starts with the code that was withdrawn from ISO 3166-1.

Obsolete ISO 3166-1 alpha-2 codes

The following is a list of obsolete ISO 3166 two-letter country codes, included here for reference. Note that many of these codes were withdrawn before the introduction of the Domain Name System, and so were never used as top-level domains. In the following list, the old two-letter code is given first, followed by the ISO 3166-3 four-letter code. For each code, the year of withdrawal is given. Once five years have passed from the time of withdrawal the code is free to be reallocated, as has been done with AI, CS, GE and SK.