| Natalie Obermeyer (Hamburg, DE) | P280 |
| Matthias Oelze (Mainz, DE) | P111, P118, P122, P123, P93 |
| René van Oerle (Maastricht, NL) | P144 |
| Motoi Ohba (Birmingham, GB) | P275 |
| Alexander Oksche (Berlin, DE) | P253 |
| Damla Olcaydu (Vienna, AT) | P90 |
| Amanda Oldani (Pavia, IT) | P267 |
| Teoceles Olivar (Quezon City, PH) | P176 |
| Monica Olson (Rochester, US) | O34 |
| Altan Onat (Istanbul, TR) | P248 |
| Hans-Dieter Orzechowski (Berlin, DE) | P158, P253 |
| Tadeusz Osadnik (Zabrze, PL) | P141 |
| Grzegorz Oszkinis (Poznań, PL) | P191 |
| Juliane Ott (Gießen, DE) | P349 |
| Olga Ovtchinnikova (Stockholm, SE) | O229 |
| Gary Owens (Charlottesville, US) | L74 |