Hawaiian is the ancestral language of the indigenous people of the Hawaiian Islands, the Hawaiians, a Polynesian people. Hawaiian, along with English, is an official language of the State of Hawai'i. It is notable for having a small phoneme inventory (see Hawaiian alphabet, below), like many of its Polynesian cousins. Especially notable is the fact that it lacks the phoneme /t/, one of only a few languages to lack such a phoneme.

Hawaiian is an endangered language. On most of the islands, Hawaiian has been displaced by English and is no longer used as the daily language of communication. An exception is Ni'ihau which still uses Hawaiian in daily communications, because it is a privately owned island and visitation by outsiders is strictly controlled. For a variety of reasons starting around 1900, the number of first-language speakers of Hawaiian diminished from 37,000 to 1,000; half of these remaining are now in their seventies or eighties.

Efforts by Native Hawaiians to revive their ancestral language have increased in recent decades. Hawaiian language "immersion" schools are now open to children whose families want to retain (or reintroduce) Hawaiian language back into the next generation. The local NPR station features a short segment titled "Hawaiian word of the day".

Hawaiian Pidgin (also known as Hawaiian Creole) is a local form of English with borrowings from Hawaiian and Asian languages (predominantly Japanese, Chinese and Tagalog) introduced by immigrants hired to work at sugar and pineapple plantations.

The Hawaiian alphabet, called ka pī'āpā Hawai'i in Hawaiian, is a variety of the Roman alphabet created in the 19th century and used to write the Hawaiian language. Until U.S. Missionaries to Hawai'i created a written form, the language was only spoken. It consists of 12 letters and a symbol, making it one of the shortest alphabets in the world (Rotokas alphabet has one letter fewer; the Pirahã language, two fewer). Its inventory consists of the consonants /p/, /k/, /`/ or /'/ (glottal stop or ‘okina, sometimes written as an opening single quote ‘), /m/, /n/, /w/ (sometimes rendered as [v]), /l/, /h/ and the vowels /a/, /e/, /i/, /o/, /u/. The macron, called a kahakō in Hawaiian, used with vowels, both extends a vowel sound and indicates a stressed syllable. It does NOT change the vowel sound (as from short to long).