The Mazda 787 and its derivative 787B are Group C sports prototype racing cars that were developed by Japanese automobile manufacturer Mazda for use in the World Sportscar Championship, All Japan Sports Prototype Championship, and the 24 Hours of Le Mans from 1990 to 1991.

Although the 787 and 787B lacked the single lap pace of World Championship competitors such as Mercedes-Benz, Jaguar, and Porsche, as well as Japanese Championship competitors Nissan and Toyota, the 787s had reliability that allowed them to contend for their respective championships.

The reliability of the cars eventually paid off in 1991 when a 787B driven by Johnny Herbert, Volker Weidler, and Bertrand Gachot went on to victory in the 1991 24 Hours of Le Mans. As of 2023, this remains the only victory by a car not using a reciprocating engine design. It was the first victory by a Japanese manufacturer, and the only such victory until Toyota won the 2018 24 Hours of Le Mans.

The first 787 chassis made its competition debut in April 1990, at the second round of the All Japan Sports Prototype Championship (JSPC) season. For the Inter Challenge Fuji 1000 km, Mazdaspeed entered their 787 alongside an older 767B chassis, with Yoshimi Katayama, David Kennedy, and Pierre Dieudonné in the new car. After Fuji, the second 787 chassis was completed, and the team departed for Europe to prepare for Le Mans.

Today the car is considered by Mazda and Wankel enthusiasts as one of the most iconic race cars to come out of Japan. It has appeared in several video games, such as the Gran Turismo series, the Forza Motorsport series, and Assetto Corsa. In 2005, a factory-backed RX-8 used the Renown colours to compete in a 24-hour race at Silverstone.

Mazda keeps the winning car at the Mazda Museum in Hiroshima. At the same time, Mazda produced two replicas and gave one of them to the Le Mans Museum. The Le Mans Museum car, chassis 04, is an authentic car with non-operational mechanics.

The engineers at Mazdaspeed determined that fuel efficiency was crucial for achieving victory so they restricted the redline of the engine to 8,500 rpm thus reducing the power output to 650 hp. Emphasis was put on high cornering speeds rather than attaining high top speeds at the straight sections of the track.