| octrooi | patent |
| Octrooi op software | Software patent |
| oculair | ocular |
| oculairlens | ocular |
| oculeren | inoculate |
| oculist | ophthalmologist |
| oculiste | ophthalmologist |
| Ocumare de la Costa de Oro | Ocumare de la Costa de Oro |
| Oda Nobunaga | Oda Nobunaga |
| Oda van Brabant | Saint Oda |
| Odaawaag | Ottawa |
| Odaenathus | Odaenathus |
| Odaiba | Odaiba |
| Odalisk | Venus |
| Odd Girl Out | Odd Girl Out |
| Odd Grenland | Odd Grenland BK |
| Odd Hassel | Odd Hassel |
| Odd-eyed | Odd-eyed cat |
| Odda | Odda |
| Oddaprocedé | Nitrophosphate process |
| Odder | Odder municipality |
| Odderade | Odderade |
| Odds ratio | Odds ratio |
| ode | ode |
| Ode an die Freude | Ode to Joy |
| Oded Fehr | Oded Fehr |
| Odeion | Odeon Records |
| Odeion van Herodes Atticus | Odeon of Herodes Atticus |
| Odelzhausen | Odelzhausen |
| Odense | Odense |
| Odense BK | Odense Boldklub |
| Odenthal | Odenthal |
| Odenwald | Odenwald |
| Odenwaldkreis | Odenwaldkreis |
| Odeon Records | Odeon Records |
| Oder | Oder |
| Oder-Havel-kanaal | Oder-Havel Canal |
| Oder-Neissegrens | Oder-Neisse line |
| Oder-Spree | Oder-Spree |
| Oderaue | Oderaue |
| Oderberg | Oderberg |
| Oderhaf | Szczecin Lagoon |
| Odernheim am Glan | Odernheim am Glan |
| Odessa | Odessa |
| Odie | Odie |
| Odiel Defraeye | Odile Defraye |
| Odilia | Odile |
| Odilo van Beieren | Odilo of Bavaria |
| Odilon Redon | Odilon Redon |
| Odin | Odin |
| Odisheim | Odisheim |
| Odo | Odo |
| Odo I van Frankrijk | Odo of France |
| Odo van Aquitanië | Odo the Great |
| Odo van Cluny | Odo of Cluny |
| Odo van Doornik | Odo of Cambrai |
| Odo van Nevers | Eudes of Burgundy |
| Odo van Toulouse | Odo of Toulouse |
| Odoaker | Odoacer |
| Odoardo Farnese | Odoardo Farnese |
| Odolanów | Odolanów |
| odometer | odometer |
| Odon | Odon River |
| Odontoblast | Odontoblast |
| Odontophorinae | New World quail |
| Odorheiu Secuiesc | Odorheiu Secuiesc |
| Odra Wodzisław | Odra Wodzisław |
| Odranci | Odranci |
| odyssee | Odyssey |
| Odysseus | Odysseus |
| Odýsseas Elýtis | Odysseas Elytis |
| Oe | Oe |
| Oebisfelde | Oebisfelde |
| Oechsen | Oechsen |
| Oechta | Ukhta |
| Oecophoridae | Oecophoridae |
| oecumenisch | ecumenical |
| Oecumenisch patriarchaat van Constantinopel | Ecumenical Patriarchate of Constantinople |
| Oecussi-Ambeno | Oecussi-Ambeno |
| Oed-Öhling | Oed-Öhling |
| Oedai Hoessein | Uday Hussein |
| Oedatsjnajapijp | Udachnaya pipe |
| Oedatsjny | Udachny |
| oedeem | edema |
| Oedegeïers | Udege people |
| oedemateus | dropsical |
| Oederan | Oederan |
| Oederquart | Oederquart |
| Oedheim | Oedheim |
