| 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 |
| oldest | mayor |
| Oldest child | Eldest |
| oldfashioned | anticuado |
| Oldfield Thomas | Oldfield Thomas |
| Oldham | Oldham |
| oldish | mayor |
| Oldly | Antigua |
| Oldman River | Río Oldman |
| Oldowan | Olduvayense |
| Oldschool jungle | Jungle |
| oldster | viejo |
| Olduvai Gorge | Garganta de Olduvai |
| Olduvai theory | Teoría de Olduvai |
| Olduwan | Olduvayense |
| Oldřich Duras | Oldřich Duras |
| Oldřich Nejedlý | Oldřich Nejedlý |
| Ole Bull | Ole Bull |
