Waikuri (Guaycura, Waicura) is an extinct language of southern Baja California spoken by the Waikuri or Guaycura people. The Jesuit priest Baegert documented words, sentences and texts in the language between 1751 and 1768.

Waikuri may be, along with the Yukian and Chumashan languages and other languages of southern Baja such as Pericú, among the oldest languages established in California, before the arrival of speakers of Penutian, Uto-Aztecan, and perhaps even Hokan languages. All are spoken in areas with long-established populations of a distinct physical type.^[1]

The ethnonym Waikuri and its variants likely originates from the Pericú word guaxoro 'friend'. Variations of the name include Waicuri, Waicuri, Guaicuri, Waicura, Guaycura, Guaicura, Waicuro, Guaicuro, Guaycuro, Vaicuro, Guaicuru, Guaycuru, Waikur.^[2]: 187

Baegert's data is analyzed by Raoul Zamponi (2004). On existing evidence, Guaycura appears to be unrelated to the Yuman languages to its north. Some linguists have suggested that it belonged to the widely scattered Hokan phylum of California and Mexico (Gursky 1966; Swadesh 1967); however, the evidence for this seems inconclusive (Laylander 1997; Zamponi 2004; Mixco 2006). William C. Massey (1949) suggested a connection with Pericú, but the latter is too meagerly attested to support a meaningful comparison. Other languages of southern Baja are essentially undocumented, though people have speculated from non-linguistic sources that Monqui (Monquí-Didiú), spoken in a small region around Loreto, may have been a 'Guaicurian' language, as perhaps was Huchití (Uchití), though that may have actually been a variety of Guaycura itself (Golla 2007).

The internal classification of Guaicurian (Waikurian) languages is uncertain. Massey (1949), cited in Campbell (1997:169), gives this tentative classification based on similarity judgments given by colonial-era sources, rather than actual linguistic data.

However, Laylander (1997) and Zamponi (2004) conclude that Waikuri and Pericú are unrelated.

Phonology of the Waikuri language:^[3]

The little we know of Guaycura grammar was provided by Francisco Pimentel, who analyzed a few verbs and phrases. Guaicura was a polysyllabic language that involved a lot of compounding. For example, 'sky' is tekerakadatemba, from tekaraka (arched) and datemba (earth).

Beagert and Pimentel agree that the plural is formed with a suffix -ma. However, Pimentel also notes a prefix k- with the 'same' function. For example, kanai 'women', from anai 'woman'. According to Pimentel, the negation in -ra of an adjective resulted in its opposite, so from ataka 'good' is derived atakara 'bad'.

Pronouns were as follows (Golla 2011):

The Pater Noster is recorded in Guaycura, with a literal gloss by Pimentel (1874: cap. XXV).

Waikuri vocabulary from Zamponi (2004), which was compiled primarily from 18th-century sources by Johann Jakov Baegert,^[4] as well as from Lamberto Hostell and Francisco de Ortega:^[2]