|Native to||United States|
|Region||Southern Oregon and northern California|
|Ethnicity||170 Klamath and Modoc (2000 census)|
|Extinct||2003, with the death of Neva Eggsman|
Klamath (//), also Klamath–Modoc (/ /) and historically Lutuamian (//), is a Native American language spoken around Klamath Lake in what is now southern Oregon and northern California. It is the traditional language of the Klamath and Modoc peoples, each of whom spoke a dialect of the language. By 1998, only one native speaker remained, and by 2003, this last fluent Klamath speaker who was living in Chiloquin, Oregon, was 92 years old. As of 2006 there were no fluent native speakers of either the Klamath or Modoc dialects; however, as of 2019, revitalization efforts are underway with the goal of creating new speakers.
Klamath is a member of the Plateau Penutian language family, which is in turn a branch of the proposed Penutian language family. Like other proposed Penutian languages, Plateau Penutian languages are rich in ablaut, much like Indo-European and Afro-Asiatic languages. Further evidence for this classification includes some consonant correspondences between Klamath and other alleged Penutian languages. For example, the Proto-Yokuts retroflexes */ʈ ʈʼ/ correspond to Klamath /tʃ tʃʼ/, and the Proto-Yokuts dentals */t̪ t̪ʰ t̪ʼ/ correspond to the Klamath alveolars /t tʰ tʼ/.
|Close||i ~ ɪ||iː|
|Open-mid||æ ~ ɛ||æː||ɔ ~ u||oː|
|Open||ə ~ ɑ||ɑː|
Obstruents in Klamath, except for /s/, /h/ and /ʔ/, all come in triplets of unaspirated, aspirated, and ejective sounds. Sonorant triplets are voiced, voiceless, and "laryngealized" sounds.
Most consonants can be geminated. The fricative /s/ is an exception, and there is evidence suggesting this is a consequence of a recent sound change. Albert Samuel Gatschet recorded geminated /sː/ in the late 19th century, but this sound was consistently recorded as degeminated /s/ by M. A. R. Barker in the 1960s. Sometime after Gatschet recorded the language and before Barker did the same, */sː/ may have degeminated into /s/.
Klamath word order is conditioned by pragmatics. There is no clearly defined verb phrase or noun phrase. Alignment is nominative–accusative, with nominal case marking also distinguishing adjectives from nouns. Many verbs obligatorily classify an absolutive case. There are directive and applicative constructions.