ISO 3166-2:GB

ISO 3166-2:GB is the entry for the United Kingdom in ISO 3166-2, part of the ISO 3166 standard published by the International Organization for Standardization (ISO), which defines codes for the names of the principal subdivisions (e.g., provinces or states) of all countries coded in ISO 3166-1. The codes and structures used are provided to the ISO by British Standards and the Office for National Statistics.

Currently for the United Kingdom, ISO 3166-2 codes are defined for the following subdivisions:
 * England:
 * 27 two-tier counties
 * 32 London boroughs
 * 36 metropolitan districts
 * 55 unitary authorities (includes 5 single-tier counties; Cornwall, Durham, Northumberland, Shropshire & Wiltshire )
 * 1 city corporation (i.e., the City of London)
 * Northern Ireland: 26 district council areas
 * Scotland: 32 council areas
 * Wales: 22 unitary authorities

Each code consists of two parts, separated by a hyphen. The first part is GB, the ISO 3166-1 alpha-2 code of the United Kingdom. The second part is three letters, which is the British Standard BS 6879 three-letter code of the subdivision.

The four constituent parts of the United Kingdom, i.e., England, Northern Ireland, Scotland, and Wales (whose status is described as either "country", or "province"), are also assigned codes, as well as three other geopolitical terms which are "included for completeness":
 * England and Wales (consisting of England and Wales)
 * Great Britain (consisting of England, Scotland, and Wales)
 * United Kingdom (consisting of England, Northern Ireland, Scotland, and Wales)

Each code consists of three letters, which is also taken from BS 6879.

The ISO 3166-1 alpha-2 code UK is also exceptionally reserved for the United Kingdom on the request of the country. Its main usage is the .uk internet ccTLD.

Current codes
Subdivision names are listed as in the ISO 3166-2 standard published by the ISO 3166 Maintenance Agency (ISO 3166/MA).

BS 6879 gives alternative name forms in Welsh (cy) for some of the Welsh unitary authorities (together with alternative code elements). Since this part of ISO 3166 does not allow for duplicate coding of identical subdivisions, such alternative names in Welsh and code elements are shown for information purposes only in square brackets after the English name of the subdivision.

Three countries and one province
Wales was changed from being described as a principality to being described as a country in the December 2011 update to the standard. England and Scotland were maintained as country and Northern Ireland was maintained as province.

Changes
The following changes to the entry have been announced in newsletters by the ISO 3166/MA since the first publication of ISO 3166-2 in 1998: