Most of the languages in the Solomon Islands archipelago are Austronesian languages, more precisely Oceanic. They belong to different language subgroups within the Oceanic family:
The Reefs – Santa Cruz languages were once thought to be non-Austronesian, but further research found them to be divergent Austronesian languages. The neighbouring languages of Vanikoro are also heavily relexified Austronesian languages. Both RSC and Vanikoro-Utupua languages are now subsumed under the Temotu subgroup of Oceanic.
Two other language families are represented on Bougainville, which forms part of the nation of Papua New Guinea but is geographically part of the archipelago.
Tryon, Darrell T.; Hackman, Bryan D. (1983). Solomon Islands languages: an internal classification. Canberra: Pacific Linguistics. doi:10.15144/PL-C72.
Data set derived from Tryon & Hackman (1983): Greenhill, Simon, & Robert Forkel. (2019). lexibank/tryonsolomon: Solomon Islands Languages (Version v3.0). Zenodo. doi:10.5281/zenodo.3535809