Äiwoo (/ˈeɪ.woʊ, ˈaɪ.-/, AY-woh, EYE-) is an Oceanic language spoken on the Santa Cruz Islands and the Reef Islands in the Temotu Province of the Solomon Islands.

The Äiwoo language has been known under many names in the literature, including: Aŷiwo, Ayiwo, Aïwo, Gnivo, Lanlom, Lomlom, Naaude, Nifilole, Nivo, Reef Islands, and Reefs.

Äiwoo has roughly 8,400 native speakers with roughly 5,000–6,000 of these living on the Reef islands and the rest living on the Santa Cruz islands. As such, Äiwoo is the largest of the Reef Islands – Santa Cruz languages. Most speakers live on the Ngawa and Ngäsinue islands in the Reef Islands; others live in some villages on Vanikoro or on Nendö, like Kala Bay. Finally, some communities have recently been established in the capital Honiara, notably in the White River district.

On the Reef islands, Äiwoo is the primary language spoken by all of its people. Most of them also speak Pijin, the lingua franca of the Solomon Islands, while only a few people also speak English. The schooling system uses Äiwoo on the primary and secondary school level, though a standardized orthography for Äiwoo has not yet been adopted, resulting in a decline of people who can read and write.

Äiwoo uses a variation of the Latin alphabet. The following spelling conventions are taken from Næss’ dictionary of Äiwoo.

Nouns are used to describe a person, place or thing. Nouns in Äiwoo can be paired with a suffix to show a possessive case. An example of this is tumo 'my father'. Other nouns in Äiwoo can be followed by a possessive particle, as in kuli nou 'my dog'.^{[citation needed]}

Bound nouns are one subtype of nouns; they act like nouns but cannot be used by themselves and need to be paired with a verb, possessive case, or another noun instead.

Local nouns are another subtype of nouns, but are not like regular nouns because they can be used to indicate location without a preposition.