Kilwa Sultanate in the context of "Kilwa District"

Mombasa (/mɒmˈbæsə/ mom-BASS-ə; also US: /-ˈbɑːsə/ -⁠BAH-sə) is a coastal city in southeastern Kenya along the Indian Ocean. It was the first capital of British East Africa, before Nairobi was elevated to capital status in 1907. It now serves as the capital of Mombasa County. Buildings in the CBD are blue and white, representing the Indian Ocean. It is the country's oldest (c. 900 A.D.) and second-largest city after Nairobi, with a population of about 1,208,333 people according to the 2019 census.

Mombasa's location on the Indian Ocean made it a historical trading centre, and it has been controlled by many countries because of its strategic location. Kenyan school history books place the founding of Mombasa as 900 AD. It must have been already a prosperous trading town in the 12th century, as the Arab geographer al-Idrisi mentions it in 1151. It was a part of the Kilwa Sultanate from approximately the early 14th century until the dissolution of the sultanate in 1513. The oldest stone mosque in Mombasa, Mnara, was built c. 1300. The Mandhry Mosque, built in 1570, has a minaret that contains a regionally specific ogee arch. The city later came under the occupation and control of the Omani Empire in the late 17th century.

Sultan Ali ibn al-Hassan Shirazi (Persian: علي بن حسن شيرازی; c. 10th century) was the founder of the Kilwa Sultanate. According to legend, Ali ibn al-Hassan Shirazi was one of seven sons of the Emir Al-Hassan of Shiraz, Persia, his mother an Abyssinian slave. Upon his father's death, Ali was driven out of his inheritance by his warring brothers. Setting sail out of Hormuz, Ali ibn al-Hassan, his household and a small group of followers first made their way to Mogadishu, a commercial port on the East African coast. However, Ali failed to get along with the city's Somali elite and he was soon driven out of that city as well.

Steering down the African coast, Ali is said to have purchased the island of Kilwa from the local Bantu inhabitants. According to one chronicle, Kilwa was originally owned by a mainland Bantu king Almuli and connected by a small land bridge to the mainland that appeared in low tide. The king agreed to sell it to Ali ibn al-Hassan for as much colored cloth as could cover the circumference of the island. But when the king later changed his mind, and tried to take it back, they had dug up the land bridge, and Kilwa was now an island.