| Name | Sailor ID | Most Recent Declaration |
|---|---|---|
| Dan O'Grady | IRLDO99 | 91.0kg - Amateur |
| Dan O'Grady | IRLD099 | |
| Trudy O'hare | IRLTO24 | 60.0kg - Amateur |
| Ewan O'Keeffe | IRLEO32 | 85.0kg - Amateur |
| Will Oldroyd | GBRWO10 | 95.0kg - Professional |
| Anthony O'Leary | IRLAO2 | 85.0kg - Amateur |
| Nicholas O'Leary | IRLNO7 | 94.0kg - Professional |
| Peter O'Leary | IRLPO17 | |
| Robert O'Leary | IRLRO31 | 85.0kg - Amateur |
| Gabriele Olivo | ITAGO1 | |
| Sebastian Olsen | DENSO5 | 88.0kg - Professional |
| Jochem Oostenbroek | NEDJO5 | 85.0kg - Amateur |
| Jessye Opoku-ware | GBRJO39 | 95.0kg - Amateur |
| Sean O'Rourke | AUSSO9 | 77.0kg - Professional |
| Clive O'Shea | IRLCO15 | 67.0kg - Amateur |
| Michael O'sullivan | IRLMO73 | 79.0kg - Amateur |
| Rory O'Sullivan | IRLRO22 | 81.0kg - Amateur |
| Mike Owen | GBRMO32 | 77.0kg - Amateur |
| Tuds Owen | GBROO2 | 102.0kg - Amateur |
| Harry Owens | GBRHO6 | |
| Harry Owens | GBRHO7 | 91.0kg - Amateur |
| James Oxenham | GBRJO29 | 85.0kg - Amateur |
| Bilge kerem Ozkan | TURBO8 | 88.0kg - Amateur |
| Marc Pajot | FRAMP99 | 88.0kg - Amateur |
| Andrew Palfrey | AUSAP06 | 103.0kg - Professional |