The history of Islam in East Africa stretches back to around 1000 CE. Until the mid-20th century, it remained largely confined to the coast and closely bound up with the history of the Swahili towns situated on it. The Swahili language remains central to many East African Muslims, hence the occasionally heard phrase, “Swahili Islam.” East African Muslims are mostly Shafiites and some belong to Sufi orders, especially Qadiriyya and Shadhiliyya. Since c. 1850, Islam, with many variations in ritual, has become the religion of speakers of a multitude of languages across the region, second only to Christianity. The region’s independent nation-states initially promised equality for all religions within a secular order. Since c. 1990, though, the minority status of East African Muslims has fed into a multitude of grievances related to the region’s economic and political impasses. This situation has led to growing movements of Islamic preaching and activism, supported by increased contacts with congregations elsewhere in the Indian Ocean. At times, they have influenced electoral politics, especially in Zanzibar, where Islamic activism resonates with fear of marginalization by the mainland. In Kenya, Somali-influenced Islamist terrorists committed a series of atrocities in the 2010s. East African governments, in turn, have been proactive in tracking and disrupting such networks, and in Kenya, the government engaged in targeted assassination. Nevertheless, peaceful coexistence between Muslims and adherents of other religions remains the norm in East Africa, and its dynamics are often poorly understood.