Are there any famous black mathematicians?
By famous, I mean in the sense of having a theorem or well-known result named after them.
David Blackwell is one of the creators of the Rao-Blackwell Theorem.
Banyaga's theorem on the group of Hamiltonian diffeomorphisms of a closed surface was mentioned here. Banyaga is a black mathematician. Banyaga's article proving this is very influential by mathematical standards: it is cited over 80 times at MathSciNet.