Born in Alès, Dumas began karting in 1992. He competed in the French Formula Renault Championship in 1996 and the French Formula 3 Championship from 1998. He tested Formula 3000 machinery for Oreca in 1999, a Renault Formula 1 car in 2002, and a Conquest Racing Champ Car in 2004, but elected to pursue single-seater formulas no further, competing instead in Euro Formula 3000 in 2001 and 2002 before committing to sports cars.
From 2001 onwards Dumas participated in every 24 Hours of Le Mans, an extraordinary streak of consecutive appearances. He became a Porsche factory driver in 2004, an association he has maintained alongside other manufacturer commitments. For Porsche and Penske Racing he competed in the American Le Mans Series, where in 2007 he dominated the LMP2 class with eight wins and four pole positions in the Penske Porsche RS Spyder.
In 2008 Dumas took an outright P2 class and overall victory at the 12 Hours of Sebring with Penske. When Roger Penske lost sports car sponsorship for 2009, Dumas and Timo Bernhard transferred on loan to Audi Sport Team Joest, and in 2010 the pairing, now joined by Mike Rockenfeller, won the 24 Hours of Le Mans outright in an Audi R15 TDI Plus. He also won the 2010 24 Hours of Spa in a Porsche 911 GT3 RSR.
Dumas returned to Porsche's LMP1 programme for the FIA World Endurance Championship era. In 2016, driving the Porsche 919 Hybrid alongside Neel Jani and Marc Lieb, he won the 6 Hours of Silverstone and the 24 Hours of Le Mans, and the trio claimed the Drivers' Championship. The Le Mans victory in 2016 was followed just days later by his second Pikes Peak overall win.
Dumas has built a parallel record at Pikes Peak that ranks among the most distinguished in the event's history. He claimed his first overall victory there in 2014 in a purpose-built Norma M20 prototype developed by his own operation, RD Limited. A second overall win followed in 2016 — the week after his Le Mans victory — again in a Norma prototype. A third overall victory came in 2017, once more in a Norma.
In 2018 Dumas drove the Volkswagen I.D. R electric prototype to a fourth overall victory, setting a new outright Pikes Peak record of 7 minutes 57.148 seconds at an average speed of 150.9 km/h, shattering the previous benchmark. The following year in the same car he set a new electric vehicle lap record at the Nürburgring Nordschleife with a time of 6:05.336, and also set a new lap record at the Goodwood Festival of Speed hill climb. In 2019 the Volkswagen I.D. R established the benchmark for the Tianmen Mountain road in China.
He claimed a further Time Attack class win at Pikes Peak in 2021 in a Porsche 911 GT2 RS Clubsport and his fifth overall victory in 2024 driving a Ford F-150 Lightning SuperTruck, finishing with a time of 8:53.563.
After the conclusion of Porsche's LMP1 programme, Dumas continued in endurance competition with a variety of programmes. He raced with Alpine at the 2017 24 Hours of Le Mans and subsequently with Rebellion Racing and Scuderia Cameron Glickenhaus in the top Hypercar and LMP1 class of the FIA WEC, recording a podium at the 2022 1000 Miles of Sebring and a pole position at the 2022 6 Hours of Monza.
In December 2023 Dumas set the world record for land vehicle altitude, driving a Porsche 911 to the peak of the west ridge of the Ojos del Salado volcano in Chile at 6,734 metres above sea level. His private operation RD Limited, founded in 2008 as the RD Rally Team, has expanded to design Group R-GT rally cars, the Norma M20 hill climb prototype, and since 2024 has competed in the Asian Le Mans Series, making its debut at the 24 Hours of Le Mans in 2026.
Romain Dumas occupies an unusual position in modern motorsport as a driver whose achievements span the world's greatest endurance races, the most demanding hill climb on the calendar, and a series of outright land vehicle records in electric prototypes. His partnership with Porsche over two decades, combined with works stints at Audi and Volkswagen, reflects an ability to adapt to multiple manufacturers and machinery at the highest level. The combination of Le Mans, Nürburgring 24 Hours, Sebring, and multiple Pikes Peak victories places him in the rarest company of all-round endurance specialists.