People who have competed at Australian Brazilian jiu-jitsu and grappling events. Australia only, for now. See Australian BJJ rankings for recorded wins by belt, state, and ruleset.
| Oskar Beck | Blue | Gracie Botany |
| Oskar Draeger | Unknown belt | Apex MMA, Muay Thai & Jiu-Jitsu |
| Oskar Hardinge | Unknown belt | Flying Squirrel Jiu-Jitsu |
| Oskar Molan | White | Integrated MMA HQ |
| Oskar Prpic | Grey | Gracie Barra Carlton |
| Oskar Stam | Yellow | Garra Brazilian Jiu Jitsu Australia |
| Oskar Taylor | White | Costa Academy |
| Oskar Wortmann | White | Ringside Gym Berlin |
| Osmaan Imran | Blue | TFC - The Fight Centre |
| Osman Dursoy | Black | Royal Empire Martial Arts (REMA) |
| Osman Hassan | White | ONYX Brazilian Jiu Jitsu |
| Osman Shaikh | White | Apex Brazilian Jiu Jitsu |
| Oswald Rudkin | Yellow | Mildura Brazilian Jiu Jitsu |
| Otakar Husar | Blue | Gold Coast Brazilian Jiu-Jitsu |
| Otamar Vieira Barreto Junior | Black | TRINITY Australia |
| Otavio Krarup Frias | Unknown belt | One Purpose BJJ |
| Otávio Serafim | Black | Grappling Bros / GFTeam |
| Otis Antreou | Blue | Peninsula MMA |
| Otis Barber | Grey | Gracie Barra Surfers Paradise |
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