| Ludger Obergassel (Bielefeld) | P1048, P435, V558 |
| Natalie Obermeyer (Hamburg) | P408, V522 |
| Erwin Oechslin (Zürich, CH) | V1681 |
| Michael Oeff (Brandenburg) | H1512, V860 |
| Hellmut Oelert (Mainz) | V253 |
| Emanuel Oepangat (Bad Oeynhausen) | P1109 |
| Frank Oertel (Augsburg) | V590 |
| Niels Oesingmann (Erlangen) | P811, V15 |
| Cemil Özcelik (Berlin) | P398, V1568 |
| Burcin Özüyaman (Düsseldorf) | P453, V626 |
| Hidemasa Oh (Houston) | P1364 |
| Harm Ohlmeier (Potsdam) | V860 |
| Thomas Oikonomopoulos (Solingen) | P1382, V552 |
| Olaf Oldenburg (Essen) | V28, V865 |
| Horst Olschewski (Gießen) | A881 |
| Eric Olson (Dallas, US) | V560 |
| Gustav Oltmanns (Sömmerda) | P178 |
| Heyder Omran (Bonn) | I368, P434, V977, V978 |
| Robert Oostendorp (München) | P101 |
| Christina Opasich (Rhoon, NL) | V1690 |
| Thomas Opfermann (Jena) | V1250 |
| Brian O'Rourke (Baltimore, US) | V516 |
| Jasmin Ortak (Lübeck) | P784, V258 |
| Michelle Ortak (Hamburg) | P1112 |
| Jan Ortlepp (Aachen) | V648 |
| Jan Ortlepp (Aachen) | H561, P1045, V1527, V1528 |
| Magdalene Ortmann (Hannover) | P452 |
| Hans-Dieter Orzechowski (Berlin) | V10, V290 |
| Brigitte Osswald (Heidelberg) | V1650 |
| Mir Ostad (Hamburg) | V850 |
| Stefan Ostermayer (Frankfurt am Main) | P449, P450 |
| Karl-Josef Osterziel (Berlin) | P398, V5 |
| Karl-Josef Osterziel (Berlin) | P1389, P1393, V1568, V4, V701 |
| Karl-Josef Osterziel (Berlin) | H1619, H1622 |
| Ilka Ott (München) | P101, P1369, V1530 |
| Rainer Ott (Krefeld) | P98 |
| Jürgen Otte (Bad Nauheim) | P204 |
| Feifan Ouyang (Hamburg) | P118, P726, P776, V1282, V1561, V1646 |
| Stanislav Ovroutski (Berlin) | P1086 |