| Ludger Obergassel (Bielefeld) | P103, P145, P146, P657, V890, V915 |
| Martin Oberhoffer (München) | V925 |
| Katja Oberholzer (Mainz) | P671 |
| Peter Oberst (Wiebaden) | V236 |
| Michael Oeff (Brandenburg) | V290 |
| Matthias Oelze (Hamburg) | P127, P128 |
| Pranobe Oemrawsingh (Leiden, NL) | P1035 |
| Arne Östman (Stockholm, SE) | P412 |
| Pitt Oetjen (Hannover) | P711 |
| Ulrich Oetjen (Frankfurt) | V1532 |
| Stefan Oettel (Leipzig) | P734 |
| Cemil Özcelik (Berlin) | A1421, P1020 |
| Lars Ohl (Hannover) | V85 |
| Harm Ohlmeier (Potsdam) | V290 |
| Marc Ohlow (Bad Berka) | P1245 |
| Darlington Okonko (London, GB) | P436, V1207, V1210 |
| Lars Olaison (Göteborg, SE) | P440 |
| Olaf Oldenburg (Bad Oeynhausen) | P702, V819 |
| Michael Olivier (Milwaukee, US) | V221 |
| Manfred Olschewski (Freiburg) | P1273 |
| Heike Olthoff (Berlin) | P955 |
| Heyder Omran (Bonn) | I1101, I1363, P659, V240 |
| William ONeill (Royal Oak, US) | P1035 |
| Andrew Ong (Rotterdam, NL) | I1070b |
| Andrew Ong (Rotterdam, NL) | V1477 |
| Thomas Opfermann (Jena) | V651 |
| Ulrich Opfermann (Leipzig) | V924 |
| Jan Opherk (Heidelberg) | P1027 |
| Andreas Opitz (Würzburg) | V1405 |
| Margot Oppacher (Bad Nauheim) | V555 |
| Brian O'Rourke (Baltimore, US) | V610 |
| Jasmin Ortak (Lübeck) | P163, P98, V1202, V1204, V23 |
| Michelle Ortak (Hamburg) | P658 |
| Jan Ortlepp (Aachen) | P135, P442 |
| Brigitte Osswald (Heidelberg) | V1215 |
| Stefan Osswald (Basel, CH) | P947, V40 |
| Mir Ostad (Mainz) | V856 |
| Hartmut Oster (Rotenburg a.d.Fulda) | V1571 |
| Stefan Osternayer (Frankfurt) | V1469 |
| Karl Osterziel (Berlin) | P1020, P198, P422, P423, V1182 |
| Karl-Josef Osterziel (Berlin) | A1422, A1522, H1155 |
| Melanie Oswald (München) | V927 |
| Svetlana Oustanina (Halle) | V633 |
| Feifan Ouyang (Hamburg) | V1434, V520, V522, V602, V606, V879, V883 |