ISO 3166-3 is an international standard that defines codes for outdated ISO 3166-1 country codes and is part of ISO 3166.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

• merged (e.g. East and West Germany)
• split up (e.g. Czechoslovakia)
• changed the main part of their name

the codes were withdrawn from ISO 3166-1 and with addition of two letters put in ISO 3166-3.

ISO 3166-3 is four-digit-alphabetic and starts with the code that was withdrawn from ISO 3166-1.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 Note that many of these codes were withdrawn before the introduction of the Domain Name System, and so were never used as top-level domains.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.

• AI - AIDJ - 1977 French Territory of the Afars and the Issas. Replaced by DJ (for Djibouti). Note that AI has since been reassigned to Anguilla.
• BQ - BQAQ - 1979 British Antarctic Territory. Now covered by AQ (Antarctica).
• BU - BUMM - 1989 Burma. Replaced by MM (for Myanmar).
• CS - CSHH - 1993 Czechoslovakia. Replaced by CZ and SK. Note that CS is now assigned to Serbia and Montenegro (Srbija i Crna Gora).
• CT - CTKI - 1984 Canton and Enderbury Islands. Now covered by KI (Kiribati).
• DD - DDDE - 1990 East Germany. Now covered by DE (Germany).
• DY - DYBJ - 1977 Dahomey. Replaced by BJ (for Benin).
• FQ - FQHH - 1979 French Southern and Antarctic Territories. Now covered by AQ and TF.
• FX - FXFR - 1997 Metropolitan France. Covered by FR (France).
• GE - GEHH - 1979 Gilbert and Ellis Islands. Now covered by KI (Kiribati) and TV (Tuvalu). Note that GE has since been reassigned to Georgia.
• HV - HVBF - 1984 Upper Volta (Haute-Volta). Replaced by BF (for Burkina Faso).
• JT - JTUM - 1986 Johnston Island. Now covered by UM.
• MI - MIUM - 1986 Midway Atoll. Now covered by UM.
• NH - NHVU - 1980 New Hebrides. Replaced by VU (for Vanuatu).
• NQ - NQAQ - 1983 Queen Maud Land. Now covered by AQ (Antarctica).
• NT - NTHH - 1993 Neutral Zone between Saudi Arabia (SA) and Iraq (IQ).
• PC - PCHH - 1986 Trust Territory of the Pacific Islands. Replaced by FM, MH, MP and PW.
• PU - PUUM - 1986 U.S. Miscellaneous Pacific Islands. Now covered by UM.
• PZ - PZPA - 1980 Panama Canal Zone. Now covered by PA (Panama).
• RH - RHZW - 1980 Rhodesia. Replaced by ZW (for Zimbabwe).
• SK - SKIN - 1975 Sikkim. Now covered by IN (India). Note that SK has since been reassigned to Slovakia.
• SU - SUHH - 1992 Soviet Union. Replaced by AM, AZ, BY, EE, GE, KG, KZ, LT, LV, MD, RU, TJ, TM, UA and UZ (of which BY and UA already existed). SU is still in use as a top-level domain.
• TP - TPTL - 2002 East Timor. Replaced by TL on becoming the independent country of Timor-Leste. TP is still in use as a top-level domain.
• VD - VDVN - 1977 Democratic Republic of Vietnam. Now covered by VN (Viet Nam).
• WK - WKUM - 1986 Wake Island. Now covered by UM.
• YD - YDYE - 1990 South Yemen. Now covered by YE (Yemen).
• YU - YUCS - 2003 Yugoslavia. Replaced by CS (for Serbia and Montenegro; Srbija i Crna Gora). YU is still in use as a top-level domain.
• ZR - ZRCD - 1997 Zaire. Replaced by CD (for Democratic Republic of the Congo).

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