Shirazi Arab clans dominated Comorian life socially, culturally, and politically from the fifteenth century until the French occupation in 1886. Eleven clans lived on Ngazidja, where their power was strongest. They divided Ngazidja into eleven sultanates and Nzwani into two. Their leaders, the sultans or sharifs, were in a continual state of war.

The descendants of clan nobles continue to form a major portion of the educated and propertied classes of Comoros. The rivalry of two political parties pre-independence was seen by some as clan antagonisms. At the same time, many descendants of nobles live in poverty and apparently have less influence socially and politically on Nzwani than on Ngazidja. The present-day elite is mainly defined in terms of wealth rather than descent.

The Shirazi, who originated from the city of Shiraz in what is now Iran, were Sunni Muslims adhering to the legal school of Muhammad ibn Idris ash Shafii, an eighth-century Meccan scholar who followed a middle path in combining tradition and independent judgment in legal matters. The Shirazi Arabs traveled and traded up and down the East African coast and as far east as India and Maldives. They maintained wives at different trading posts, this being most likely the origin of polygamy in Comoros.

The Shirazi built mosques and established Islam as the religion of the islands. They also introduced stone architecture, carpentry, cotton weaving, the cultivation of certain fruits, and the Persian solar calendar. By the sixteenth century, Shirazis had made Comoros a center of regional trade.