O
| O.J. | Oki | Oops | Osiris |
| Oakley | Okki | Opie | Oskar |
| Oasis | Oklahoma | Opoe-s | Osman |
| Obelix | Olaf | Oprah | Oswald |
| Obie | Olga | Oprheus | Ot |
| Obi-Wan Kenobi | Oliebol | Opus | Othello |
| Octavia | Olijf | Oral | Otis |
| Oda | Olin | Orange | Otje |
| Odan | Olive | Orbie | Otter |
| Odd | Oliver | Orco | Ottie |
| Odie | Olivia | Orfeus | Otto |
| Odin | Olivier | Orion | Oursa |
| Odius | Ollie | Orlando | Owen |
| Ody | Ollin | Oropher | Oxbow |
| Odysseus | Olly | Orphée | Oxford |
| Odyssey | Omega | Orry | Ozzie |
| Oedipus | Onassis | Orville | Ozzy |
| Oezewoes | Onawa | Orwell | |
| Offel | Onix | Osama | |
| Oidipoes | Onnie | Oscar | |
| Ojee | Onyx | Oscy |