| O associations | Association O |
| O Baixo Miño | O Baixo Miño |
| O Canada | Ô Canada |
| O clusters | Amas O |
| O come all ye faithful | Adeste Fideles |
| O Dragão da Maldade Contra o Santo Guerreiro | Antonio Das Mortes |
| O dwarf stars | Etoile O naine |
| O Fantasma | O Fantasma |
| O giant stars | Etoile O geante |
| O Holy Night | Minuit Chrétiens |
| O le Ao o le Malo | O le Ao O le Malo |
| O Little Town of Bethlehem | O Little Town of Bethlehem |
| O magnitude | Magnitude O |
| O Pagador de Promessas | La Parole donnée |
| O Sanctissima | O Sanctissima |
| O stars | Etoile o |
| O subdwarf stars | Etoile O sous naine |
| O supergiant stars | Etoile O supergeante |
| O Tannenbaum | Mon beau sapin |
| O Tempo e o Vento | Le Temps et le Vent |
| O-Bahn Busway | Autobus guidé |
| O-seal | Joint torique |
| O-yatoi gaikokujin | Oyatoi gaikokujin |
| O-Zone | O-Zone |
| oaf | lourdaud |
| oafish | lourdaud |
| Oahu | Oahu |
| Oahu Island | Oahu Island |
| oak | chêne |
| Oak fungus | Chêne |
| Oak Park | Oak Park |
| Oak Processionary | Processionnaire du chêne |
| oak tree | chêne |
| Oak wood | Chêne |
| oaken | de chêne |
| Oakland | Oakland |
| Oakland California | Oakland |
| Oakmont | Oakmont |
| Oakmoss | Lichen |
| oakum | étoupe |
| Oakville | Oakville |
| oar | rame |
| oarlock | dame de nage |
| oarsman | rameur |
| oarswoman | rameuse |
| OAS | Organisation des Etats Américains |
| oasis | oasis |
| oast | sécherie à houblon |
| oasthouse | sécherie à houblon |
| oat | avoine |
| oatcake | galette d'avoine |
| oath | vœu |
| Oath Against Modernism | Sacrorum Antistitum |
| Oath of Abjuration | Acte de La Haye |
| Oath of Hippocrates | Serment d’Hippocrate |
| Oath of the Horatii | Le Serment des Horaces |
| Oath taking | Prestations de serment |
| Oaths of Strasbourg | Serments de Strasbourg |
| oatmeal | bouillie d'avoine |
| oats | avoine |
| Oaxaca | État d'Oaxaca |
| Ob | Ob |
| OB associations | Association OB |
| Ob River | Ob |
| OB stars | Etoile OB |
| OB supergiant stars | Etoile OB supergeante |
| Obadiah | Abdias |
| Obadiah ben Jacob Sforno | Ovadia Sforno |
| Obaidullah Akhund | Obaidullah Akhund |
| Obaku | Ôbaku |
| Obala | Obala |
| Obalno-kraška | Obalno-kraška |
| Oban | Oban |
| Oban Distillery | Oban |
| Obatala | Oxalá |
| Obduction | Obduction |
| Obdulio Varela | Obdulio Varela |
| Obdurodon | Obdurodon dicksoni |
| obedience | soumission |
| obedient | bien élevé |
| obediently | respectueusement |
| obeisance | révérence |
| Obelerio degli Antenori | Obelerio Antenoreo |
| obelisk | obélisque |
| Obelisk of Buenos Aires | Obélisque de Buenos Aires |
| Obelix | Obélix |
| Oben am jungen Rhein | Oben am jungen Rhein |
| Ober Gabelhorn | Obergabelhorn |
| Ober Rengersdorf | Ober Rengersdorf |
| Ober-Ramstadt | Ober-Ramstadt |
| Oberammergau | Oberammergau |
| Oberbalm | Oberbalm |
| Oberbergischer Kreis | Haut-Berg |
| Oberbipp | Oberbipp |
| Oberbuchsiten | Oberbuchsiten |
| Oberburg | Oberburg |
| Oberbözberg | Oberbözberg |
| Oberbüren | Oberbüren |
| Oberdiessbach | Oberdiessbach |
| Oberdorf | Oberdorf |
