| oilskins | impermeable de hule |
| oily | aceitoso |
| Oily fish | Pescado azul |
| oink | gruñir |
| ointment | pomada |
| ointment for burns | ungüento para quemaduras |
| Oireachtas | Oireachtas |
| Oise | Oise |
| Oise River | Río Oise |
| Oita Trinita | Oita Trinita |
| Ojamajo Doremi | Magical Doremi |
| Ojos Así | Ojos así |
| Ojos del Salado | Ojos del Salado |
| OK | bien |
| OK Go | Ok Go |
| Oka cheese | Río Oká |
| Oka River | Río Oká |
| Okane ga nai | Okane ga Nai |
| okapi | okapí |
| Okarito Brown Kiwi | Apteryx rowi |
| Okavango Delta | Okavango |
| Okavango Region | Kavango |
| Okavango River | Okavango |
| okay | bien |
| Okayama | Okayama |
| Okayama Prefecture | Prefectura de Okayama |
| okays | propicio |
| Okazaki fragment | Fragmento de Okazaki |
| OKB | OKB |
| Okhotsk Plate | Placa de Okhotsk |
| Okhranka | Ojrana |
| Okinawa | Isla de Okinawa |
| Okinawa Churaumi Aquarium | Acuario Churaumi |
| Okinawa Island | Isla de Okinawa |
| Okinawa Prefecture | Prefectura de Okinawa |
| Okinawan language | Idioma okinawense |
| Okinotorishima | Okino Torishima |
| Okita Sōji | Okita Sōji |
| Oklahoma | Oklahoma |
| Oklahoma - Oklahoma City | Estado de los Estados Unidos de América |
| Oklahoma City | Oklahoma City |
| Oklahoma City bombing | Atentado de Oklahoma City |
| Oklo | Oklo |
| Okondo | Oquendo |
| Okonomiyaki | Okonomiyaki |
| okra | quingombó |
| Okroshka | Okroshka |
| Oktoberfest | Oktoberfest |
| Okurigana | Okurigana |
| Olaberria | Olaberría |
| Olaf I of Denmark | Olav I de Dinamarca |
| Olaf I of Norway | Olaf I de Noruega |
| Olaf II of Norway | Olaf II el Santo |
| Olaf III of Norway | Olaf III de Noruega |
| Olaf Magnusson of Norway | Olaf Magnusson de Noruega |
| Olaf Stapledon | Olaf Stapledon |
| Olancho | Olancho |
| OLAP cube | Cube |
| Olaus Magnus | Olaus Magnus |
| Olaus Rudbeck | Olaus Rudbeck |
| Olav | Olaf el Tesorero |
| Olav IV of Norway | Olaf II de Dinamarca |
| Olav V of Norway | Olaf V |
| Olavarría Partido | Olavarría |
| Olbendorf | Olbendorf |
| Olbia | Olbia |
| old | viejo |
| old age | vejez |
| old age pensioner | rentista |
| Old Castile | Castilla la Vieja |
| Old Catholic Church | Iglesia Católica Antigua |
| Old Catholic Church of Austria | Iglesia Católica Antigua |
| Old Catholic Mission in France | Iglesia Católica Antigua |
| Old Church Slavonic | Antiguo eslavo eclesiástico |
| Old City | Ciudad Vieja de Jerusalén |
| Old City of Jerusalem | Ciudad Vieja de Jerusalén |
| Old Dominion | Virginia |
| Old English | Idioma anglosajón |
| Old English language | Idioma anglosajón |
| Old European Script | Escritura Vinča |
| Old Faithful Geyser | Old Faithful |
| old fashioned | anticuado |
| old folks' home | asilo de ancianos |
| Old growth forest | Pluvisilva |
| Old Gutnish | Gútnico antiguo |
| old hazardous site | antiguo sitio peligroso |
| Old Indian Defense | Defensa india antigua |
| Old Italic alphabet | Alfabeto etrusco |
| Old Kingdom | Imperio Antiguo de Egipto |
| old landfill site | vertedero antiguo |
| old man | vieja |
| Old Man and the Sea | El viejo y el mar |
| Old materials | Derribos |
| Old Montreal | Vieux-Montreal |
| Old New Synagogue | Sinagoga Vieja-Nueva |
| Old Norse | Nórdico antiguo |
| Old Norse language | Nórdico antiguo |
| Old Norwegian | Noruego antiguo |
| Old Nosy | Wellington |
| Old people | Parsonas mayores |
| old people's home | asilo de ancianos |
| Old Port of Montreal | Vieux-Port de Montreal |
| Old Prussia | Prusia |
| Old Prussian | Idioma prusiano antiguo |
| Old Prussians | Prusia |
| Old Saxon | Sajón antiguo |
| Old school hip hop | Old school rap |
| Old Slavic | Antiguo eslavo eclesiástico |
| Old star | Estrella vieja |
| Old Swiss Confederacy | Antigua Confederación Suiza |
| Old Tbilisi | Ciudad Vieja de Jerusalén |
| Old Testament | Viejo Testamento |
| Old Town of Prague | Ciudad Vieja de Jerusalén |
| Old Trafford | Old Trafford |
| Old Tupi language | Lenguas tupí |
| Old World | Viejo Mundo |
| Old World flycatcher | Muscicapidae |
| Old World monkey | Cercopithecidae |
| Old World porcupine | Hystricidae |
| Old World Swallowtail | Papilio machaon |
| Old World vulture | Aegypiinae |
| Old World warbler | Sylviidae |
| Old Zürich War | Antigua Guerra de Zúrich |
| old-established | antiguo |
| old-fashioned | anticuado |
| old-time | antiguo |
| old-timer | coche antiguo |
| Oldboy | Oldboy |
| olden | envejecer |
| Oldenburg | Oldenburgo |
| older | mayor |
