| Oregon Trail | Oregon Trail |
| Oregonterritorium | Oregon Territory |
| Orel | Orel |
| Orellana | Orellana Province |
| Orenburg | Orenburg |
| Orenburg Airlines | Orenburg Airlines |
| Orendain | Orendain |
| oreren | declaim |
| Oresteia | The Oresteia |
| Orestes | Orestes |
| Orestie | The Oresteia |
| Orexa | Orexa |
| Orff-Schulwerk | Orff Schulwerk |
| Orfgen | Orfgen |
| orgaan | organ |
| Orgaan van Jacobson | Vomeronasal organ |
| Organel | Organelle |
| organiek | organic |
| Organisasi Papua Merdeka | Free Papua Movement |
| organisatie | setup |
| Organisatie van Afrikaanse Eenheid | Organisation of African Unity |
| Organisatie van Amerikaanse Staten | Organization of American States |
| Organisatie van de Islamitische Conferentie | Organization of the Islamic Conference |
| Organisatie van Ibero-Amerikaanse landen | Organization of Ibero-American States |
| Organisatie van Niet-gebonden Landen | Non-Aligned Movement |
| Organisatie van Werelderfgoedsteden | Organization of World Heritage Cities |
| Organisatie voor Economische Samenwerking en Ontwikkeling | Organisation for Economic Co-operation and Development |
| Organisatie voor het Verbod op Chemische Wapens | Organisation for the Prohibition of Chemical Weapons |
| Organisatie voor Veiligheid en Samenwerking in Europa | Organization for Security and Co-operation in Europe |
| Organisation Todt | Organisation Todt |
| organisator | organizer |
| organisator van revivals | revivalist |
| organisatorisch | organizational |
| organisatrice | organizer |
| organisatrice van revivals | revivalist |
| organisch | organic |
| Organische architectuur | Organic architecture |
| Organische chemie | Organic chemistry |
| Organische Licht Emitterende Diode | Organic light-emitting diode |
| Organische lichtemitterende diode | Organic light-emitting diode |
| Organische synthese | Organic reaction |
| Organische verbinding | Organic compound |
| organiseren | arrange |
| organisme | body |
| organist | organist |
| organiste | organist |
