| Brian O'NEILL | IRL | 9 Races |
| Liv OBEL | DEN | 7 Races |
| Ákos OBERT | HUN | 7 Races |
| Mykola OCHKUR | UKR | 16 Races |
| Ryan OCONNOR | IRL | 5 Races |
| Eka OCTARORIANUS | INA | 9 Races |
| Morosan OCTAVIAN | ROU | 3 Races |
| Liudmila ODINTSOVA | RUS | 15 Races |
| Ioannis ODYSSEOS | CYP | 33 Races |
| Lisa OEHL | GER | 3 Races |
| Yul OELTZE | GER | 18 Races |
| Hannes OESTERLE | GER | 8 Races |
| Max TEN OEVER | NED | 4 Races |
| Elling OFTEDAL | NOR | 9 Races |
| Asumi OHMURA | JPN | 17 Races |