Roger De Coster (born 28 August 1944 in Uccle) is a Belgian former world champion motocross racer and current motocross team manager.
De Coster's name is almost synonymous with the sport of motocross, winning five 500cc Motocross World Championships during the 1970s and tallying a record 36 500cc Grand Prix victories.[2] His stature is such in the world of motocross that he is often simply referred to as "The Man."

De Coster began his professional motocross career with the Czechoslovakian firm ČZ racing in the 500cc class. He was also competent in other forms of off-road motorcycling, winning a Gold Medal in the 1964 International Six Days Trial, and won the 1964 Belgian Observed Trials National Championship. He won the 500cc Belgian National Championship in 1966 and moved up to the Grand Prix World Championship in 1967. He won his first 500cc Grand Prix in 1968.

In 1971, De Coster left ČZ and join the Japanese firm Suzuki. It was with Suzuki that he would attain his greatest success, winning the 500cc Motocross World Championship three years in a row in 1971, 1972 and 1973 before Heikki Mikkola dethroned him in 1974. De Coster came back and regained the World Championship for the 1975 and 1976 seasons. By the mid-seventies, he had established himself as the greatest motocrosser of all time. In 1980, He joined Honda for one final season. He left the sport on top, winning his final world championship race — the 500cc Motocross Grand Prix of Luxembourg at the end of the 1980 season. He was also a four-time winner of the Trans-AMA motocross series and was a member of six winning Belgian teams in the Motocross des Nations.

De Coster was known for his smooth, controlled riding style and a commitment to physical training. His training regime gave him the stamina that allowed him to circulate for most of the race in mid-pack before putting in a late charge through the field to victory when other racers had begun to tire.

After his racing career, De Coster moved to the U.S. and remained involved in the sport, becoming the motocross team manager for Honda and Suzuki. Starting in 2011, he will be the team manager for the Red Bull KTM team. He has also managed Team USA in the Motocross of Nations.