Nelson Dieppa (born February 25, 1971) is a Puerto Rican professional boxer. As an amateur, he represented Puerto Rico in international events including the 1991 World Amateur Boxing Championships, 1991 Pan American Games and the 1992 Summer Olympics. Dieppa debuted as a professional on February 13, 1993, when he defeated Carlos Figueroa. His first world championship fight took place on July 3, 2000, when he lost to Will Grigsby for the World Boxing Organization's light flyweight championship.