Tanganyika /ˌtæŋɡənˈjiːkə/ was a sovereign state that existed from 1961 until 1964. It was situated between the Indian Ocean and the African Great Lakes of Lake Victoria, Lake Nyasa and Lake Tanganyika. It gained independence from the United Kingdom as a Commonwealth realm on 9 December 1961, becoming a republic within the Commonwealth of Nations exactly a year later, on 9 December 1962. From 1962 to 1964 it was officially called the Republic of Tanganyika. On 26 April 1964, Tanganyika joined with the People's Republic of Zanzibar and Pemba to form the United Republic of Tanganyika and Zanzibar, a new state that changed its name to the United Republic of Tanzania within a year.
Tanganyika originally consisted of the Tanganyika Territory, the British share of German East Africa, which the British took under a League of Nations Mandate in 1922, and which was later transformed into a United Nations Trust Territory after World War II. The other parts of German East Africa were taken into Belgian trusteeship, eventually becoming present-day Rwanda and Burundi.
The Tanganyika Independence Act 1961 transformed the United Nations trust territory into the independent sovereign Commonwealth realm of Tanganyika. The British monarch Elizabeth II remained head of state and Tanganyika shared the Sovereign with the other Commonwealth realms. The monarch's constitutional roles were mostly delegated to the Governor-General of Tanganyika. The royal succession was governed by the English Act of Settlement of 1701.
Tanganyika adopted a new constitution in 1962 that abolished the monarchy. Tanganyika became a republic within the Commonwealth.