A proper understanding of inshore marine ecosystems cannot be obtained without a thorough knowledge of marine vegetation. This paper summarises our knowledge of species diversity patterns of marine macroalgae in Sub-Saharan Africa, highlighting gaps. In Tropical East Africa the seaweed floras of Somalia and Mozambique are not well known. In Tropical West Africa, only a small number of countries are well-collected, although recent advances, including web-based systems, are ensuring that the information which is available can be more easily accessed. South Africa and Namibia have quite well documented seaweed floras, although detailed collections, especially in the subtidal, or detailed studies of taxa, particularly using molecular methods, anywhere in the region are likely to bring up new records and lead to the discovery of species new to science. South Africa has a very rich seaweed flora (ca. 850 species), due to the presence of species from three of the four major biogeographic regions in sub-Saharan Africa occurring within its borders.