I think a company named after "De Beers" or called "Anglo American" is not what people think of when they think of an African startup. It wouldn't be seen as a triumph of African startups if all the big companies were started and run by non-Africans.

But MTN is a good example. There's also Naspers, which is not quite a startup, but which is starting to act like one. (They took a big stake in DST a couple months ago.)