Islam is the most prominent religion on the island of Zanzibar. According to the CIA Factbook, Zanzibar is more than 99% Muslim. Islam came to Zanzibar in the 10th century.

According to one source, "Islam in Zanzibar inspired anti-colonialism, political movements and nationalistic struggle for independence."

Zanzibar ( /ˈzænzɨbɑr/; from Arabic: زنجبار‎ Zanjibār, from Persian: زنگبار‎ Zangibār "Coast of Blacks"; zangi [black-skinned] + bār [coast]) is a semi-autonomous part of Tanzania, in East Africa. It comprises the Zanzibar Archipelago in the Indian Ocean, 25–50 kilometres (16–31 mi) off the coast of the mainland, and consists of numerous small islands and two large ones: Unguja (the main island, informally referred to as Zanzibar), and Pemba. Other nearby island countries and territories include Comoros and Mayotte to the south, Mauritius and Réunion to the far southeast, and the Seychelles Islands about 1,500 km to the east. Arab and Portuguese traders visited the region in early times, and it was controlled by Omanis in the 18th and 19th centuries. Britain established a protectorate (1890) that became an independent sultanate in December 1963 and a republic after an uprising in January 1964. In April 1964 it joined Tanganyika to form a new republic that was renamed Tanzania in October 1964. The capital of Zanzibar, located on the island of Unguja, is Zanzibar City, and its historic centre, known as Stone Town, is a World Heritage Site.