| oso de felpa | teddy bear |
| Oso de Oro | Golden Bear |
| oso gris | grizzly |
| oso hormiguero | anteater |
| oso hormiguero gigante | giant anteater |
| oso malayo | sun bear |
| oso marsupial | koala |
| oso negro | black bear |
| Oso Paddington | Paddington Bear |
| oso pardo | grizzly bear |
| oso polar | polar bear |
| oso viscoso | Gummy Bears |
| Oso Yogi | Yogi Bear |
| Osocor | Osorkon the Elder |
| Osogna | Osogna |
| Osorkon I | Osorkon I |
| Osorkon II | Osorkon II |
| Osorkon III | Osorkon III |
| Osorkon IV | Osorkon IV |
| Osos Amorosos | Care Bears |
| Osphronemidae | Gourami |
| Osram | Osram |
| Osric de Deira | Osric of Deira |
| Osroene | Osroene |
| Ossian | Ossian |
| Ossip Bernstein | Ossip Bernstein |
| Ossip Zadkine | Ossip Zadkine |
| Ossobuco | Ossobuco |
| Ossolineum | Ossolineum |
| Ostalgie | Ostalgie |
| Osteichthyes | Osteichthyes |
| Ostende | Ostend |
| ostensible | ostensible |
| ostentación | boast |
| ostentar | flaunt |
| ostentosamente | ostentatiously |
| ostentoso | flashy |
| Osteofito | Bone spur |
| Osteoglossiformes | Osteoglossiformes |
| Osteointegración | Osseointegration |
| Osteolaemus tetraspis | Dwarf Crocodile |
| Osteoporosis | Osteoporosis |
| Osteospermum | Osteospermum |
| Ostermundigen | Ostermundigen |
| osteópata | osteopath |
| Ostpolitik | Ostpolitik |
| ostra | oyster |
| ostracismo | ostracism |
| Ostracon | Ostracon |
| Ostrava | Ostrava |
| Ostreidae | Ostreidae |
| Ostreoida | Ostreidae |
| ostrero | oystercatcher |
| ostricultura | oyster farming |
| Ostrogodos | Ostrogoths |
| Ostrón del Delta del Ebro | Pacific oyster |
| Ostsiedlung | Ostsiedlung |
| Ostwind | Ostwind |
| osuno | ursine |
| osupljiv | astounding |
| Osvaldo Ardiles | Osvaldo Ardiles |
| Osvaldo Dorticós Torrado | Osvaldo Dorticós Torrado |
| Osvaldo Golijov | Osvaldo Golijov |
| Osvaldo Piazza | Oswaldo Piazza |
| Osvaldo Pugliese | Osvaldo Pugliese |
| Oswald Avery | Oswald Avery |
| Oswald el conejo afortunado | Oswald the Lucky Rabbit |
| Oswald Mosley | Oswald Mosley |
| Oswald Pohl | Oswald Pohl |
| Oswald Spengler | Oswald Spengler |
| Oswaldo Guayasamín | Oswaldo Guayasamín |
| Oswaldo Guillén | Ozzie Guillén |
| Oswaldo Payá | Oswaldo Payá |
| Oswino de Deira | Oswine of Deira |
| Oswiu de Northumbria | Oswiu of Northumbria |
| Otago | Otago |
| Otakar I de Bohemia | Ottokar I of Bohemia |
| Otakar II de Bohemia | Ottokar II of Bohemia |
| Otaku no Video | Otaku no Video |
| OTAN | NATO |
| Otaniemi | Otaniemi |
| Otariidae | Eared seal |
| Otatea | Otatea |
| OTE | OTE |
| otear | scan |
| Otello | Otello |
| Otelo | Othello |
| OTEP | OTEP |
| OTF | OTF |
| Otfried Preussler | Otfried Preußler |
| Otherland | Otherland |
| Othniel Charles Marsh | Othniel Charles Marsh |
| Othnielia | Othnielia |
| Othnielosaurus | Othnielosaurus |
| Otis Redding | Otis Redding |
| Otis tarda | Great Bustard |
| otitis | otitis |
| Otmar Hasler | Otmar Hasler |
| Otmar Suitner | Otmar Suitner |
| oto ada | fall |
| otoe | cocoyam |
| otomano | ottoman |
