Actually, that would be the Bantu. But the Bantu were not very unified, many would argue that there weren't really a civilization but just a language group (same goes for the Swahili). Personally I'd prefer the Zimbabwians or Mali. The former were from roughly the same region as the Zulu (Zimbabwe is actually the capital of the Zulu in Civ3

) while they most certainly were a single unified and important civilization while the latter were IMHO one of the most important (and most underestimated) civilizations in the history of mankind (not as important as the Romans or Chinese but still in the top 16).