The development of Swahili literature is profoundly marked by the dual nature of this African language. On the one hand, it is the mother tongue of the Swahili communities, located mainly on the coast of Kenya and Tanzania and on the adjacent islands, and on the other hand, it is a vehicular language that spread to large inland regions of East and Central Africa, initially through the caravan trade that flourished in the 19th century, then due to missionary and colonial activities, and after independence thanks to the language policies of the new nations. A local, national and transnational language, therefore, and a language that embraces different religious worlds, from the Islam of coastal communities and Islamised inland areas to Christianity, whose evangelisation in mainland regions was mainly based on Swahili. This composite literary universe will be outlined in the essay, highlighting some theoretical and critical points.