Kumaoni (Kumaoni-Devanagari: कुमाऊँनी, pronounced [kuːmaːʊ̃ːniː]) is an Indo-Aryan language spoken by over two million people of the Kumaon region of the state of Uttarakhand in Northern India, Sudurpashchim Province & Karnali Province in Western Nepal. As per 1961 survey there were 1,030,254 Kumaoni speakers in India. The number of speakers increased to 2.0 million in 2011.

Kumaoni is not endangered but UNESCO's Atlas of the World's Languages in Danger designates it as a language in the unsafe category, meaning it requires consistent conservation efforts.

Kumaoni is written using the Devanagari script.

There are several dialects spoken in the Kumaon region. There is not single accepted method of dividing up the dialects of Kumaoni. Broadly speaking, Kali (or Central) Kumaoni is spoken in Almora and northern Nainital. North-eastern Kumaoni is spoken in Pithoragarh. South-eastern Kumaoni is spoken in South-eastern Nainital. Western Kumaoni is spoken west of Almora and Nainital.

More specifically:

Some Kumaoni speakers are also reportedly found in Western Nepal.

Various Kumaoni text have been found from the Katyuri and Chand era on temple stones and as copper plate inscriptions. Kumaoni was also the official language of the Kumaon Kingdom.^{[citation needed]}

Being part of the Indo-Aryan dialect continuum Kumaoni shares its grammar with other Indo-Aryan languages like Dotyali, Nepali, Hindi, Rajasthani, Kashmiri and Gujarati. It shares much of its grammar with the other language of the Central Pahari group like Garhwali. The peculiarities of grammar in Kumaoni and other Central Pahari languages exist due to the influence of the now extinct language of the Khasas, the first inhabitants of the region. In Kumaoni the verb substantive is formed from the root ach, as in both Rajasthani and Kashmiri. In Rajasthani its present tense, being derived from the Sanskrit present rcchami, I go, does not change for gender. But in Pahari and Kashmiri it must be derived from the rare Sanskrit particle *rcchitas, gone, for in these languages it is a participial tense and does change according to the gender of the subject. Thus, in the singular we have: - Here we have a relic of the old Khasa language, which, as has been said, seems to have been related to Kashmiri. Other relics of Khasa, again agreeing with north-western India, are the tendency to shorten long vowels, the practice of epenthesis, or the modification of a vowel by the one which follows in the next syllable, and the frequent occurrence of disaspiration. Thus, Khas siknu, Kumaoni sikhno, but Hindi sikhna, to learn; Kumaoni yeso, plural yasa, of this kind.