Khmu [kʰmuʔ] is the language of the Khmu people of the northern Laos region. It is also spoken in adjacent areas of Vietnam, Thailand and China. Khmu lends its name to the Khmuic branch of the Austro-Asiatic language family, the latter of which also includes Khmer and Vietnamese. Within Austro-Asiatic, Khmu is often cited as being most closely related to the Palaungic and Khasic languages. The name "Khmu" can also be seen romanized as Kmhmu, Khmu', Kammu, or Khamuk in various publications or alternatively referred to by the name of a local dialect.

As a minority language with no standardizing influence, many dialects have evolved. Dialects differ primarily in consonant inventory, existence of register, and the degree to which the language has been influenced by the surrounding national language(s). Dialects are, for the most part, mutually intelligible; however communication can be difficult between speakers of geographically distant dialects.

The dialects of Khmu can be broadly categorized into two groups, Western Khmu and Eastern Khmu. Western Khmu dialects have fewer consonant phonemes and instead use phonemic register contrast, as seen in other Austro-Asiatic languages, of "lax" breathy register and "tense" modal register. In at least one dialect of Western Khmu, known as Khmu Rook, tonogenesis is evident as the register contrast has developed into a system of two phonetic tones with six phonemic realizations. Eastern Khmu dialects show the opposite tendency. Completely lacking either register or tone distinction, these dialects utilize a three-way distinction of stops (voiced, voiceless and aspirated voiceless) and nasals (voiced, voiceless, and pre-glottalized) in the syllable-initial position for phonemic contrast.

The Khmu ( /kəˈmuː/; also spelled Khamu or Kemu; Khammu or Khơ Mú in Vietnam; Lao: ຂະມຸ [kʰámū]; Thai: ขมุ) is one of the largest ethnic groups based in northern Laos. They can also be found in Burma, southwest China (in the Sipsong Panna in Yunnan province), Thailand, Vietnam, and Richmond, California, where they are an officially recognized ethnic group. In the People's Republic of China, however, they are not given official recognition as a separate ethnic group, and are instead placed under the broad category undistinguished ethnic groups.

The Khmu (also referred to as Khamu, Kammu or Kemu) were the indigenous inhabitants of northern Laos. There are more than 500,000 Khmu around the world, with populations of 450,000 in Laos, 43,000 in Vietnam, 10,000 in Thailand, 10,000 in China, and 8,000 in the United States.^{[citation needed]} The Khmu of Laos reside mainly within the Luang Prabang and Xieng Khouang Provinces. The Khmu of Thailand are clustered near the Thailand-Laos border. Most Khmu villages are isolated, and only slowly receiving electricity. In many areas the Khmu live alongside the Hmong and other regional minority ethnic groups. A large number of Khmu live in Richmond, California, having come as refugees from the Vietnam War. California is home to both the Khmu National Federation, Inc., and the Kmhmu Catholic National Center. Most Khmu in Thailand arrived recently from Laos and Vietnam as refugees, also around the outset of the Vietnam War. The Khmu, however, are closely related to the Mlabri, the indigenous yellow leaf people of Thailand.