ISO 3166-2:IO

ISO 3166-2:IO is the entry for the British [Indian Ocean Territory] in ISO 3166-2, part of the ISO 3166 standard published by the International [Organization for Standardization], which defines codes for the names of the principal subdivisions of all countries coded in ISO 3166-1.
Currently no ISO 3166-2 codes are defined in the entry for the British Indian Ocean Territory. The territory has no defined subdivisions.
The British Indian Ocean Territory is officially assigned the ISO 3166-1 alpha-2 code. Diego Garcia, its largest island, is exceptionally reserved the ISO 3166-1 alpha-2 code on the request of the International [Telecommunication Union].