| O | Oline (Germany) | Osprey (GB) |
| (O. T. Moe) (Norway) | Olive (GB) | Ost (Russia) |
| Oak (GB) | Ollanta (Peru) | Ostana I (Sweden) |
| Oakdale (GB) | Olli (Finland) | Ostara (Germany) |
| (Oberbaurat Schmidt) (Germany) | Olympia (USA) | (Oste) (Netherlands) |
| Oberon III (Finland) | Olympian (Chile) | Oster (Norway) |
| Occidental (USA) | (Omar) (USA) | (Ostergarn) (Sweden) |
| (Oceaan I) (Netherlands) | Ondee (France) | Ostersund (Sweden) |
| (Ocean) (Germany) | Ongarue (New Zealand) | (Osuukunta I) (Finland) |
| Ocean Hawk II (Canada) | Onslow (Australia) | Otago (Australia) (USA) |
| Ocean Mist (GB) | (Onverschrokken) (Netherlands) | Othello (New Zealand) |
| (Ocean Rover) (GB) | Onyx (GB) | Otso (Finland) |
| Ocean Waif (USA) | Oosterschelde (Netherlands) | (Otso) (Finland) |
| Oceanor (France) | Opreisningen (Norway) | Otto (GB) |
| Ocelot (GB) | Oregon (USA) | Otto Lauffer (Germany) |
| (Odette) (Netherlands) | Orinoco (GB) | Oudenaarde (Belgium) |
| (Odin) (Norway) | (Orivest II) (Finland) | Our Lady of Lourdes (Canada) |
| (Olandsrev) (Sweden) | (Orthona) (Sweden) | Our Svanen (Australia) |
| Old Barge Cafe (USA) | Oscar Huber (Germany) | (Outer Gabbard) (Netherlands) |
| (Old Lady) (Germany) | Oscar Tybring I (USA) | Ovens (Australia) |
| Old Point (USA) | Oscar W. (Australia) | Overfalls (USA) |
| (Oldenburg) (Finland) | Oseberg Viking Ship (Norway) | (Overfalls) (USA) |
| Olga (GB) | Osmo (Finland) | Owhiti (New Zealand |
