| Organische chemie | Organisk kemi |
| Organische stof | Organisk materiale |
| Organische verbinding | Organisk forbindelse |
| organisme | organisme |
| orgasme | orgasme |
| orgel | orgel |
| Orgelvogels | Svalestære |
| Orhan Pamuk | Orhan Pamuk |
| Oriana Fallaci | Oriana Fallaci |
| Orichalcum | Messing |
| Oriente | Orienten |
| Oriflamme | Oriflamme |
| Origanum | Merian |
| Origenes | Origenes |
| Original Six | Original Six |
| origineel | ægte |
| Orinoco | Orinoco |
| Orion | Orion |
| Orionnevel | Oriontågen |
| Orissa | Orissa |
| Oriënt-Express | Orientekspressen |
| Oriëntaals-orthodoxe Kerken | De ortodokse kirker |
| Oriëntatieloop | Orienteringsløb |
| Orjol | Ørnen |
| Orjol-klasse | Ørnen |
| orkaan | orkan |
| Orkdal | Orkdal |
| Orkney-eilanden | Orkneyøerne |
| Orkut | Orkut |
| Orlando Bloom | Orlando Bloom |
| Orlando di Lasso | Orlando di Lasso |
| Orléans | Orléans |
| Ormen Lange-gasveld | Ormen hin Lange |
| Ornithomimus | Ornithomimus |
| Ornitopter | Ornitopter |
| Orodruin | Dommedagsbjerget |
| Orpheus | Orfeus |
| Orphée | Orfeus |
| Orsa | Orsa |
| Orsasjön | Orsasjön |
| Orson Scott Card | Orson Scott Card |
| Orson Welles | Orson Welles |
| Orthodox christendom | Ortodoks |
| Orthodox jodendom | Ortodoks jødedom |
| Orthodoxe Kerk | De ortodokse kirker |
| Orthodoxe kerken | Ortodoks |
| Orthorexia nervosa | Ortoreksi |
| Orthosie | Orthosie |
| orthosympatisch zenuwstelsel | sympatiske nervesystem |
| Orto botanico di Padova | Padovas botaniske have |
| Orvieto | Orvieto |
| Orwelliaans | Orwellsk |
| os | stud |
| Os trapezium | Trapez |
| Osaka | Osaka |
| Osama bin Laden | Osama bin Laden |
| Osamu Tezuka | Osamu Tezuka |
| Osby | Osby kommun |
| Oscar | Oscar |
| Oscar Bernadotte | Oscar Bernadotte |
| Oscar Camenzind | Oscar Camenzind |
| Oscar Gutierrez | Rey Mysterio |
| Oscar Niemeyer | Oscar Niemeyer |
| Oscar Peterson | Oscar Peterson |
| Oscar Wilde | Oscar Wilde |
| Oscilloscoop | Oscilloskop |
| Oseltamivir | Tamiflu |
| Osen | Osen |
| Osgiliath | Osgiliath |
| OSI-model | OSI-model |
| Osijek | Osijek |
| Osip Mandelstam | Osip Mandelstam |
| Osiris | Osiris |
| Osiris Shoes | Osiris |
| Osj | Osj |
| Oskar Kokoschka | Oskar Kokoschka |
| Oskar Lafontaine | Oskar Lafontaine |
| Oskar Schindler | Oskar Schindler |
| Oslo | Oslo |
| Oslofjord | Oslofjorden |
| osmium | osmium |
