24. Robert Mouawad

Net Worth: $1.5 B
Age: 79
Residence: Bahrain
Nationality: Lebanese
Industry: Service

Robert Mouawad inherited the family's eponymous high-end jewelry business that his grandfather founded in Beirut in 1890. He turned over management of the business to his sons Fred, Alain, and Pascal in 2010. Mouawad boasts one of the world's most dazzling gem collections, including Dynasty, a 51.12-carat Russian diamond estimated at nearly $10 million. Robert Mouawad also owns extensive real estate and has developed luxury residences on a man-made island in Bahrain.