Kirundi or Rundi is a Bantu language with about 4.5 million speakers, most of whom live in Burundi. There are also some speakers of Kirundi in Uganda, Tanzania, Rwanda and Congo-Kinshasa. Kirundi is closely related to Kinyarwanda.
There has been a standardised spelling system for Kirundi since the 1940s. Kirundi is one of the official languages of Burundi and is spoken in most parts of the country.
Text adapted from http://www.omniglot.com/writing/kirundi.php