Zanzibar Revolution Day is observed in Tanzania every January 12, commemorating the Zanzibar Revolution of 1964. This significant holiday marks the overthrow of the Sultan of Zanzibar and his government by revolutionaries led by John Okello, who mobilized on the main island of Unguja. The revolution resulted in the African Afro-Shirazy Party gaining power, following a period of reprisals against the Arab and South Asian civilian population, leading to an estimated death toll of up to 20,000. Following the revolution, Zanzibar merged with Tanganyika in April 1964, forming modern Tanzania, with Zanzibar designated as a semi-autonomous region. The day serves as a reminder of the historical events that shaped the nation and is recognized as a public holiday in Tanzania.