ISO 639-3:2007, Codes for the representation of names of languages – Part 3: Alpha-3 code for comprehensive coverage of languages, is an international standard for language codes in the ISO 639 series. It defines three-letter codes for identifying languages. The standard was published by International Organization for Standardization (ISO) on 1 February 2007.

ISO 639-3 extends the ISO 639-2 alpha-3 codes with an aim to cover all known natural languages. The extended language coverage was based primarily on the language codes used in the Ethnologue (volumes 10–14) published by SIL International, which is now the registration authority for ISO 639-3. It provides an enumeration of languages as complete as possible, including living and extinct, ancient and constructed, major and minor, written and unwritten. However, it does not include reconstructed languages such as Proto-Indo-European.

ISO 639-3 is intended for use as metadata codes in a wide range of applications. It is widely used in computer and information systems, such as the Internet, in which many languages need to be supported. In archives and other information storage, it is used in cataloging systems, indicating what language a resource is in or about. The codes are also frequently used in the linguistic literature and elsewhere to compensate for the fact that language names may be obscure or ambiguous.