The first known inhabitants of Rwanda were the Twa. The Hutu, probably from the Congo Basin, were well established by the 15th century, when the Tutsi came down from the north and conquered the area. The Tutsi kings, or mwamis, became the absolute monarchs of the region. Their rule was enforced by chiefs and subchiefs, who each ruled an umusozi, a fiefdom that consisted of a single hill. Political and economic relations were based on an unequal feudal relationship, known as the ubuhake system, in which the Hutu became a caste of serfs forced into subjugation and economic dependency by the Tutsi. This caste system was rigidly upheld, and intermarriage was almost nonexistent. A similar feudal system was dominant in Burundi.

Tutsi traditions trace the birth of the Rwanda kingdom to the miraculous feats of its founding hero, Gihanga, whose coming to Rwanda is said to coincide with the advent of civilization. A more sober appraisal, however, would emphasize a long process of Tutsi migrations from the north, culminating in the 16th century with the emergence of a small nuclear kingdom in the central region. From 1894 to 1918, Rwanda, along with Burundi, was part of German East Africa. After Belgium became the administering authority under the mandates system of the League of Nations, Rwanda and Burundi formed a single administrative entity; they continued to be jointly administered as the Territory of Ruanda-Urundi until the end of the Belgian trusteeship in 1962. By then, however, the two states had evolved radically different political systems, with Rwanda having declared itself a republic in January 1961 and forced its monarch (mwami), Kigeri, into exile. Burundi, on the other hand, retained the formal trappings of a constitutional monarchy until 1966.

At the insistence of the United Nations trusteeship council, Belgium granted Rwanda independence on July 1, 1962, with Grégoire Kayibanda, leader of the Parmehutu (now renamed the Democratic Republican Movement; MDR), as president. The MDR won the elections in 1965 and 1969. In 1963 some exiled Tutsi returned to Rwanda as a rebel army. Although unsuccessful, the takeover attempt prompted a large-scale massacre of Tutsi by the Hutu, followed by periodic ethnic violence. At the same time thousands of Hutu victimized in Burundi took refuge in Rwanda. In July 1973 the defense minister, General Juvénal Habyarimana, led a bloodless coup that ousted Kayibanda. Habyarimana, a Hutu from the north, charged that Kayibanda favored southern Hutu and was trying to monopolize power. Both parliament and the MDR were suspended after the coup. Political activities resumed in 1975 with the formation of a new ruling party called the National Revolutionary Movement for Development (NRMD). In 1978 a new constitution was approved, and President Habyarimana was confirmed in office for another five years.