Kirundi, also known as Rundi, is a dialect of the Rwanda-Rundi language spoken by some 8.7 million people^{[citation needed]} in Burundi and adjacent parts of Tanzania and Congo-Kinshasa, as well as in Uganda. It is the official language of Burundi. (The Kinyarwanda dialect is the official language of neighboring Rwanda.)

The inhabitants of Rwanda and Burundi belong to several different ethnic groups: Hutu (84%), Tutsi, including Hima (15%), and Twa (1%) (a pygmy people). The fact that these ethnic groups share the same language is assumed to be the result of the Hutu outnumbering the latter two groups (see Hutu for a more complete historical perspective).

Neighboring dialects of Rundi are mutually intelligible with Ha, a language spoken in western Tanzania.

Rundi is frequently cited as a language where Meeussen's rule, a rule describing a certain pattern of tonal change in Bantu languages, is active.

While the literature on Rundi agrees on 5 vowels, the number of consonants can vary anywhere from 19 to 26 consonants. The table below is compiled from a survey of academic acceptance of Rundi consonants, grouping voiceless and voiced consonants together in a cell where appropriate, in that order.