Zanzibar is a semi-autonomous archipelago off the coast of Tanzania, consisting of Zanzibar Island (locally, Unguja), Pemba Island, and many smaller islands. Zanzibar island is approximately 90 km long and 30 km wide.
The island and the surrounding islets are divided into three regions. They are Zanzibar Central/South, Zanzibar North and Zanzibar Urban/West. Zanzibar City, on the central west coast, is the capital and largest city of Zanzibar and the region of Zanzibar Urban/West. The population of Unguja was about 900,000 in 2016, with the most concentrated populations in the Zanzibar Urban Region.
The larger and more populated of Zanzibar's two main islands, Unguja is separated from its northern neighbor Pemba by 48 km of open sea. The mainland of Tanzania, which lies to the southwest of Unguja and is separate from it by the Zanzibar Channel, is considerably closer, as is the major Tanzanian mainland port of Dar es Salaam. Smaller islands surround the coast, notably Tumbatu in the northwest, Uzi in the south, and Mnemba Atoll in the northeast. A considerable number of smaller islands and reefs lie off Unguja's southwest coast.