ISO 639-2:1998, Codes for the representation of names of languages — Part 2: Alpha-3 code, is the second part of the ISO 639 standard, which lists codes for the representation of the names of languages. The three-letter codes given for each language in this part of the standard are referred to as "Alpha-3" codes. There are 464 entries in the list of ISO 639-2 codes.

The US Library of Congress is the registration authority for ISO 639-2 (referred to as ISO 639-2/RA). As registration authority, the LOC receives and reviews proposed changes; they also have representation on the ISO 639-RA Joint Advisory Committee responsible for maintaining the ISO 639 code tables.

Work was begun on the ISO 639-2 standard in 1989, because the ISO 639-1 standard, which gives two-letter codes for languages, would not be able to accommodate a sufficient number of languages. The ISO 639-2 standard was first released in 1998.

While most languages are given one code by the standard, twenty of the languages described have two three-letter codes, a "bibliographic" code (ISO 639-2/B), which is derived from the English name for the language and was a necessary legacy feature, and a "terminological" code (ISO 639-2/T), which is derived from the native name for the language. Each of these twenty languages is also included in the ISO 639-1 standard. (There were 22 B codes; scc and scr are now deprecated.)