Stéphane Mertens (born 14 May 1959 in Paris, France) is a Belgian motorcycle road racer.
He made his Grand Prix debut in 1984, racing in the 250cc class. He also won the 1984 250cc Belgian Road Racing National Championship. He continued racing in the 250cc Grands Prix in 1985, 1986 and 1987. In 1988 he made the switch to racing production based motorcycles in the inaugural Superbike World Championship. Mertens raced in the Superbike class until 1994 with his best result being a second-place finish behind Fred Merkel in the 1989 season, while riding for Honda. In 1995 he began to compete in the motorcycle Endurance World Championship, winning that title in 1995 and 2002. Mertens was a member of the winning team at the 1990 24 Hours of Le Mans.