ISO 639-3 is an international standard for language codes. In defining some of its language codes, some are classified as macrolanguages, which include other individual languages in the standard. This category exists to assist mapping between another set of languages codes, ISO 639-2, and ISO 639-3. ISO 639-3 is curated by SIL International, ISO 639-2 is curated by the Library of Congress (USA).

The mapping often has the implication that it covers borderline cases where two language varieties may be considered strongly divergent dialects of the same language or very closely related languages (dialect continuums). It may also encompass situations when there are language varieties that are sometimes considered to be varieties of the same language and sometimes different languages for ethnic or political rather than linguistic reasons. However, this is not its primary function and the classification is not evenly applied. For example, "Chinese" is a macrolanguage encompassing many languages that are not mutually intelligible, but the languages "Standard German", "Bavarian German", and other closely related languages do not form a macrolanguage despite being more mutually intelligible. Other examples include Tajiki not being part of the Persian macrolanguage despite sharing much lexicon, and Urdu and Hindi not forming a macrolanguage. Basically, ISO 639-2 and ISO 639-3 use different criteria for dividing language varieties into languages, 639-2 uses shared writing systems and literature more whereas 639-3 focuses on mutual intelligibility and shared lexicon. The macrolanguages exist within the ISO 639-3 code set to make mapping between the two sets easier.

ISO 639 is a set of standards by the International Organization for Standardization that is concerned with representation of names for language and language groups.

It was also the name of the original standard, approved in 1967 (as ISO 639/R) and withdrawn in 2002. The ISO 639 set consists of five parts.

The current and historical parts of the standard

Each part of the standard is maintained by a maintenance agency, which adds codes and changes the status of codes when needed. ISO 639-6 was withdrawn in 2014.

Characteristics of individual codes

Scopes:

Types (for individual languages):