The Sultanate of Zanzibar (Swahili: Usultani wa Zanzibar, Arabic: سلطنة زنجبار, romanized: Sulṭanat Zanjībār), also known as the Zanzibar Sultanate, was an East African Muslim state controlled by the Sultan of Zanzibar, in place between 1856 and 1964. The Sultanate's territories varied over time, and after a period of decline, the state had sovereignty over only the Zanzibar Archipelago and a 16-kilometre-wide (10 mi) strip along the Kenyan coast, with the interior of Kenya constituting the British Kenya Colony and the coastal strip administered as a de facto part of that colony.

Under an agreement reached on 8 October 1963, the Sultan of Zanzibar relinquished sovereignty over his remaining territory on the mainland, and on 12 December 1963, Kenya officially obtained independence from the British. On 12 January 1964, revolutionaries, led by the African Afro-Shirazi Party, overthrew the mainly Arab government. Jamshid bin Abdullah, the last sultan, was deposed and lost sovereignty over Zanzibar, marking the end of the Sultanate, and resulted in the massacre of tens of thousands of Arabs.