The original inhabitants of Burundi were the Twa, a Pygmy people who now make up only 1% of the population. Today the population is divided between the Hutu (approximately 85%) and the Tutsi, approximately 14%. While the Hutu and Tutsi are considered to be two separate ethnic groups, scholars point out that they speak the same language, have a history of intermarriage, and share many cultural characteristics. Traditionally, the differences between the two groups were occupational rather than ethnic. Agricultural people were considered Hutu, while the cattle-owning elite were identified as Tutsi. Supposedly Tutsi were tall and thin, while Hutu were short and square, but in fact it is often impossible to tell one from the other. The 1933 requirement by the Belgians that everyone carry an identity card indicating tribal ethnicity as Tutsi or Hutu increased the distinction. Since independence, the landowning Tutsi aristocracy has dominated Burundi.

Burundi was once part of German East Africa. Belgium won a League of Nations mandate in 1923, and subsequently Burundi, with Rwanda, was transferred to the status of a United Nations trust territory. In 1962, Burundi gained independence and became a kingdom under Mwami Mwambutsa IV, a Tutsi. A Hutu rebellion took place in 1965, leading to brutal Tutsi retaliations. Mwambutsa was deposed by his son, Ntaré V, in 1966. Ntaré in turn was overthrown the same year in a military coup by Premier Michel Micombero, also a Tutsi. In 1970–1971, a civil war erupted, leaving more than 100,000 Hutu dead.

On Nov. 1, 1976, Lt. Col. Jean-Baptiste Bagaza led a coup and assumed the presidency. He suspended the constitution and announced that a 30-member Supreme Revolutionary Council would be the governing body. In Sept. 1987 Bagaza was overthrown by Maj. Pierre Buyoya, who became president. Ethnic hatred again flared in Aug. 1988, and about 20,000 Hutu were slaughtered. Buyoya, however, began reforms to heal the country's ethnic rift. The Burundi Democracy Front's candidate, Melchior Ndadaye, won the country's first democratic presidential elections, held on June 2, 1993. Ndadaye, the first Hutu to assume power in Burundi, was killed within months during a coup. The second Hutu president, Cyprien Ntaryamira, was killed on April 6, 1994, when a plane carrying him and the Rwandan president was shot down. As a result, Hutu youth gangs began massacring Tutsi; the Tutsi-controlled army retaliated by killing Hutus.

The frequency of ethnic clashes increased, developing into a low-intensity civil war. A six-nation regional proposal to send troops into Burundi to maintain peace and order was devised in July 1996. Distrustful of the scheme, the Tutsi-dominated army led a coup deposing the Hutu president and installed Maj. Pierre Buyoya that month. More than 300,000 people have been killed in the civil war since 1993, with the Tutsi-dominated army and the Hutu rebel forces responsible for the slaughter. After several aborted cease-fires, a 2001 peace plan included a power-sharing agreement that has been relatively successful: Buyoya, a Tutsi, governed the new transitional government for the first 18 months; then, in April 2003, a Hutu president, Domitien Ndayizeye, assumed power. In Aug. 2005, former Hutu rebel leader Pierre Nkurunziza was elected president by parliament. The peaceful transfer of power to a democratically elected leader seemed to indicate that Burundi's 12-year civil war was truly at an end. Peace talks between the government and Burundi's only remaining rebel group continued in 2006.