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 of National Statistics.

Currently for the United Kingdom, ISO 3166-2 codes are defined for the following subdivisions:

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":

ISO 3166-2 is part of the ISO 3166 standard published by the International Organization for Standardization (ISO), and defines codes for the names of the principal subdivisions (e.g., provinces or states) of all countries coded in ISO 3166-1. The official name of the standard is Codes for the representation of names of countries and their subdivisions – Part 2: Country subdivision code. It was first published in 1998.

The purpose of ISO 3166-2 is to establish an international standard of short and unique alphanumeric codes to represent the relevant administrative divisions and dependent territories of all countries in a more convenient and less ambiguous form than their full names. Each complete ISO 3166-2 code consists of two parts, separated by a hyphen:

Each complete ISO 3166-2 code can then be used to uniquely identify a country subdivision in a global context.

Currently more than 4000 codes are defined in ISO 3166-2. For some countries, codes are defined for more than one level of subdivisions.