Religion in Burundi is diverse, with varying estimates. According to a 2008 estimate in CIA Factbook, about 86 percent of the population of Burundi is Christian (62.1% being Roman Catholic, 23.9% being Protestant), 7.9% have no specified religion, and 2.5 percent is Muslim (mainly Sunni). In contrast, another estimate in the Encyclopedia of Africa states 67 percent of the Burundi people are Christians, 23% follow traditional religions, and 10% are Muslims.
Burundi has the highest percentage of Catholics of any country in Africa. It is one of only three countries on the continent where Catholicism is adhered to by the majority of inhabitants, the other two being its neighbors Rwanda and the Democratic Republic of the Congo.
The earliest Christian missions arrived in 1879, but the missionaries were killed and the king of Burundi who ruled through 1908 had no interest in foreign theology or imported goods.
Larger Christian missions arrived in Burundi in the early 20th century, during its German colonial rule era, and followed by its Belgian colonial rule era. Catholic and Protestant missionaries arrived in the first two decades of the 20th century, while the 1920s saw the arrival of Baptists, the 1930s the arrival of Free Methodists and Anglican missionaries. These missions were closely involved with the colonial project. In post-colonial independent Burundi, Christianity has had a deep engagement with political leaders of Burundi, a country with nearly 11 million citizens and one of the most densely populated nations in Africa (over 1000 people per square mile).
The religious institutions within Burundi have both been called upon to help heal social divisions, help end civil chaos after political assassinations, and close wounds of mass violence, but they have also been criticized. Some, such as Timothy Longman - a professor and director of the African Studies Center, state that the colonial officials and Christian missionaries assumed the people of the newly conquered lands to be "savage and anarchic", then worsened the ethnic divisions within the Burundi society by assuming that "the peoples of the world could be neatly divided into distinct racial categories and subcategories" in order to competitively convert them to Christianity. The missionaries did not invent ethnic groups, states Longman, because they pre-existed. However, they did create racial significance when these didn't exist before, inadvertently creating ideological divisions and inequalities.
Initial conversions to Catholicism in Burundi were almost exclusively among the Hutu people - the majority in Burundi but one who neither were the rulers nor were part of economic elite. In contrast, the Protestant missionaries gained early conversions in the elite but minority Tutsi people of Burundi. The assumptions about the ethnic differences, states Longman, led to discriminatory practices, questionable distribution of property. The resulting conflicts and retaliatory genocide among Hutu and Tutsi ethnic groups, in Burundi - and Rwanda with which Burundi shares history and culture - have attracted widespread dismay and attention.
In the post-colonial contemporary era, Mushasha in the Gitega Province of Burundi serves as its archbishop's seat. The traditional Catholic and Protestant community has been losing members to more emotional Evangelical Protestantism.
Islam arrived in Burundi some 200 years before Christianity through Sunni Arab-Swahili traders active in the Lake Tanganyika region. However, Islam has been a minority religion with some presence in the trading towns near the Lake. In contemporary times, political bodies and media have critiqued and questioned the destabilizing influence of Islamic preachers.
The Transitional Constitutional Act of 2001 provided for freedom of religion and this right is generally respected in practise. Religious groups must register with the Ministry of Interior and maintain a headquarters within the country. The heads of major religions are given diplomatic status. Certain Catholic holidays are observed as public holidays.