| October Revolution | Revolución de Octubre |
| Octobers | Octubre |
| Octodon | Octodon |
| Octodontidae | Octodontidae |
| Octoechos | Oktoíjos |
| Octogen | HMX |
| octogenarian | octogenario |
| Octonion | Octoniones |
| Octopous | Octopoda |
| octopus | pulpo |
| Octopus agave | Agave vilmoriniana |
| Octopus card | Tarjeta Octopus |
| Octopussy | Octopussy |
| Octopussy and The Living Daylights | Octopussy |
| octosyllabic | octosilábico |
| ocular | inmediato |
| oculist | oftalmólogo |
| Oculocerebrorenal syndrome | Síndrome de Lowe |
| Ocumare de la Costa de Oro | Municipio Ocumare de la Costa de Oro |
| Ocytocin | Oxitocina |
| OD | Óðr |
| OD-N-Aiwo Hotel | Hotel OD-N-Aiwo |
| Oda Nobunaga | Oda Nobunaga |
| Odaenathus | Septimio Odenato |
| Odaiba | Odaiba |
| odd | raro |
| Odd Grenland BK | Odd Grenland BK |
| Odd Hassel | Odd Hassel |
| odd-jobs | bricolaje |
| Odd-toed ungulates | Perissodactyla |
| Oddar Meancheay Province | Provincia de Oddar Mean Chey |
| Oddi altar | Retablo Oddi |
| oddity | singularidad |
| oddly | singularmente |
| oddness | singularidad |
| odds | probabilidad |
| Odds and Evens | Pares y nones |
| Odds ratio | Odds ratio |
| ode | oda |
| Ode to Joy | Oda a la Alegría |
| Oden | Oden |
| Odense | Odense |
| Odense Boldklub | Odense BK |
| Odense Municipality | Odense |
| Odenwaldkreis | Odenwaldkreis |
| Oder | Óder |
| Oder River | Óder |
| Oder-Neisse line | Línea Oder-Neisse |
| Oder-Spree | Distrito de Oder-Spree |
| Odessa | Odesa |
| Odessa Catacombs | Catacumbas de Odesa |
| Odessa Cubbage | Odessa Cubbage |
| Odessa Oblast | Óblast de Odesa |
| Odessa Soviet Republic | República Soviética de Odesa |
| Odet de Coligny | Odet de Coligny |
| Odile Defraye | Odile Defraye |
| Odilon Redon | Odilon Redon |
| Odin | Odín |
| odious | odioso |
| Odo de St Amand | Eudes de Saint-Amand |
| Odo of Bayeux | Odo de Bayeux |
| Odoacer | Odoacro |
| Odocoileus | Odocoileus |
| odometer | cuentakilómetros |
| Odometry | Odometría |
| Odonata | Odonata |
| Odontites | Odontites |
| Odontoblast | Odontoblasto |
| odor | olor |
| odoriferous | oloroso |
| odoriferously | oloroso |
| odorless | inodoro |
