This volume explores how the people of littoral East Africa imagined and reimagined their communities over two millennia of engagement with Indian Ocean transformations—from the settlement of Bantu speakers near the coast around the first century CE to their participation in transoceanic commerce, imperial rivalries, colonial projects, and decolonization movements in the mid-twentieth century. Like other histories of the Indian Ocean, it emphasizes the circulation of people and ideas, but its cis-oceanic approach demonstrates how these littoral communities continued to integrate strategies from those in Africa’s interior as well as from people who traveled the ocean. The book also clarifies the precise relationship between ethnicity and other kinds of identities by expanding the conventional focus on Swahili people to speakers of Sabaki Bantu languages, as well as to Mijikenda, Pokomo, and Elwana communities, whom Indian Ocean scholars often overlook. By examining all these groups’ shared linguistic heritage, the book outlines their forebears’ innovation and transformation of lineages, clans, confederations, councils, title societies, age sets, moieties, religious sects, and tribes. Drawing together evidence from linguistics, archaeology, ethnography, oral traditions, travelers’ accounts, and colonial records, the book explores how the speakers of Sabaki languages continuously reconceptualized their identities in littoral East Africa as the political topography of the Indian Ocean world changed around them. Moving seamlessly across multiple precolonial and colonial eras and beyond, this deep history of collaboration and political imagination leads readers through the transitions of identity that mattered to littoral East Africans. The book fills the need for an updated synthesis of East Africans’ engagements with diasporic communities in Indian Ocean and world history courses. In addition, since most African history publications for classroom use in recent years have focused exclusively on modern times, it satisfies the demand for works that span the early and modern eras. Beyond the classroom, the book will interest specialists in the history of the Indian Ocean, Africa, Islam, imperialism, and ethnohistory. A major contribution of this multidisciplinary work is to present the research of archaeologists, anthropologists, linguists, and historians to one another in an accessible, jargon-free manner. While Africanists will appreciate how the book expands the boundaries of the Indian Ocean to include oft-ignored communities, Indian Ocean specialists will find models for investigating the construction of ethnicity and other collective identities across multiple centuries.