They mainly live in Rwanda, Burundi, and Uganda where they form one of the principal ethnic groups alongside the Tutsi and the Great Lakes Twa.

Prior to 2017, the CIA World Factbook stated that 84% of Rwandans and 85% of Burundians are Hutu, with Tutsis being the second largest ethnic group at 15% and 14% of residents of Rwanda and Burundi, respectively.

[5] Mahmood Mamdani states that the Belgian colonial power designated people as Tutsi or Hutu on the basis of cattle ownership, physical measurements and church records.

However, it is unclear whether this similarity is primarily due to extensive genetic exchanges between these communities through intermarriage or whether it ultimately stems from common origins: [...] generations of gene flow obliterated whatever clear-cut physical distinctions may have once existed between these two Bantu peoples – renowned to be height, body build, and facial features.

With a spectrum of physical variation in the peoples, Belgian authorities legally mandated ethnic affiliation in the 1920s, based on economic criteria.

To some extent, the permeability of these categories in the intervening decades helped to reify the biological distinctions, generating a taller elite and a shorter underclass, but with little relation to the gene pools that had existed a few centuries ago.

[20] In 1993, Burundi's first democratically elected president, Melchior Ndadaye, who was Hutu, was believed to be assassinated by Tutsi officers, as was the person constitutionally entitled to succeed him.

[citation needed] There were many mass killings of Tutsis and moderate Hutus; these events were deemed to be a genocide by the United Nations International Commission of Inquiry for Burundi.

As of 2006[update], violence between the Hutu and Tutsi had subsided, but the situation in both Rwanda and Burundi was still tense, and tens of thousands of Rwandans were still living outside the country (see Great Lakes refugee crisis).