Pierre Buyoya (24 November 1949 – 17 December 2020) was a Burundian army officer and politician who served as the seventh president of Burundi from 1996 to 2003. Having previously served as the fifth president from 1987 to 1993, Buyoya was the second-longest-serving president in Burundian history, after Pierre Nkurunziza.

An ethnic Tutsi, Buyoya joined the sole legal party, UPRONA and quickly rose through the ranks of the Burundian military. In 1987, he led a military coup d'état that overthrew his predecessor Jean-Baptiste Bagaza and enabled him to seize power. Leading an oppressive military junta, Hutu uprisings in 1988 led to the killings of an estimated 20,000 people. Buyoya then established a National Reconciliation Commission that created a new constitution in 1992 which allowed for a multi-party system and a non-ethnic government. Running as a candidate in the 1993 Burundian presidential election, he was defeated by Hutu candidate Melchior Ndadaye of the FRODEBU opposition party.

Ndadaye was assassinated during another attempted coup after only three months in office, leading to a series of retaliatory killings that culminated in the Burundian Civil War. During the war, Buyoya returned to power in another coup d'état in 1996. During his second presidency, he created an ethnically inclusive government by establishing a partnership with FROBEDU. This led to the 2000 Arusha Accords which introduced ethnic power sharing. He selected Domitien Ndayizeye, a Hutu as his vice-president, who succeeded him as president in 2003. The war ended two years later.

Following the end of the war, Buyoya became a senator for life under the terms of the 2004 constitution. During his post-presidency, he was also sent as an African Union envoy during peace missions in Chad and Mali. In October 2020, he was sentenced to life in prison in absentia by a Burundinan court for his suspected role in the 1993 coup attempt that assassinated Ndadaye. He died of COVID-19 two months later.

Pierre Buyoya was born in Rutovu, Bururi Province, on 24 November 1949 in Belgian-administered Ruanda-Urundi. His father, Rurikumunwa, was ethnically a Tutsi-Hima of the Batyaba clan. The name "Buyoya" was not the family's surname, but instead can be translated as "baby". Buyoya later recollected that his parents had lost several other children and feared that he too might die young, thus initially picking the name "baby" for their son and deciding that they could later change the name. This decision was not unusual, as children have traditionally often received descriptive or protective names per Burundian naming customs. Despite his parents' initial intention, Buyoya's name was never updated.

He received a primary education at a Catholic mission in Rutovu from 1958 to 1963. He thereafter attended the Ecole moyenne pédagogique until 1967. He enlisted as an officer the Burundian Army and studied at the Royal Military Academy in Brussels, Belgium, rising to the rank of major. Academically, Buyoya studied social sciences, examined armoured cavalry, and defended a thesis concerning the Algerian National Liberation Front. Once done with his studies in Belgium, he attended the General Staff College in France from August 1976 to January 1977 and the Bundeswehr Command and Staff College in West Germany from 1980 to 1982.

Buyoya married Sophie Ntaraka in 1978, and the couple had four children. He entered the long-term single party, Union for National Progress (Union pour le Progrès national, UPRONA), and acquired a position on its Central Committee (Comité central) in 1979. He renewed his party membership in 1984. Buyoya joined the General Staff of the Army in 1982 and was made responsible for training. His rapid rise through the military hierarchy earned him the nickname "Old Man", and he was well-respected by his fellow soldiers. The New York Times reported in 1996 that "[n]o one could recall his ever telling a joke. He is often seen at soccer games and reads a lot. He eschews a uniform, though his leisure suits recall French summer khakis."

In September 1987, Buyoya led a military coup d'état against the regime of Jean-Baptiste Bagaza who had taken power in another coup in November 1976. Buyoya's coup was reportedly organized by non-commissioned officers who had disapproved of Bagaza's plan to limit army service to ten years and to end the soldiers' right to free electricity for living spaces outside barracks. Buyoya led the country as the chairman of a 31-person military committee of national safety. He proclaimed an agenda of economic liberalisation. As in previous regimes, he presided over an oppressive ruling junta consisting primarily of Tutsi. Initially, there were few policy changes compared to Bagaza's regime, with a notable exception being Buyoya's effort to improve relations with the Christian churches by ending the government's anti-clerical campaign.