Augustin Banyaga is a Rwandan-born American mathematician whose research fields include symplectic topology and contact geometry. He is currently a Professor of Mathematics at Pennsylvania State University. Banyaga was the first person from Rwanda to obtain a Ph.D. in mathematics.
Augustin Bizimungu (born 28 August 1952) was a Rwandan military general and one of the main perpetrators of the Rwandan Genocide. He was found guilty for war crimes and is currently in prison.
I don't think you can pronounce it the French way unless you're French, because the endings in -in are not pronounced like the feminine in -ine. Augustin is a very old name.
A famous bearer of this name (which can also be pronounced aw-GUS-tin or AW-gus-tin) is Augusten Burroughs, the #1 bestselling author. His books include "Running With Scissors" and "Sellevision."