Ninteenth-Century Lake Tanganyika was a Commercial Frontier. It was a natural political boundary or barrier, a point of fracture between cultures, and a zone of transition between economic regions. It also harboured multiple different cultures that were as much characterised by their diversity as they were by their intrinsic links to the lake. It is the argument of this thesis that the nature of these features were primarily shaped by Lake Tanganyika’s role in the construction of long-distance commerce. This thesis will therefore show both how Lake Tanganyika was affected by the growth of long-distance commerce, and how it affected the machinations of long-distance commerce itself. This will be achieved by analysing migration patterns, trade, the changing nature of settlements, labour and socio-cultural change around and across Lake Tanganyika.