| Oksytocyna | Oxytocin |
| oktan | octane |
| Oktanitrokuban | Octanitrocubane |
| Oktant | Octans |
| oktawa | octave |
| Oktawia | Claudia Octavia |
| Oktawia Młodsza | Octavia Minor |
| Oktawian August | Augustus |
| Oktawy Cayleya | Octonion |
| Oktet | Byte |
| Oktoberfest | Oktoberfest |
| Oktogen | HMX |
| Oktol | Octol |
| Oktreotyd | Octreotide |
| okular | eyepiece |
| okularnik | spectacled cobra |
| okulary | glasses |
| okulary korekcyjne | glasses |
| okulary przeciwsłoneczne | sunglasses |
| okulary słoneczne | sunglasses |
| okulista | ophthalmologist |
| okulistyka | ophthalmology |
| Okulografia | Eye tracking |
| okup | ransom |
| okupacja | occupation |
| Okupacja Aliancka | Allied Occupation Zones in Germany |
| Okupacja aliancka Austrii | Allied-administered Austria |
| Okupacja wojenna | Military occupation |
| okólnik | circular mail |
| Ola Hakansson | Ola Håkansson |
| Ola Håkansson | Ola Håkansson |
| Olaf | Olaf |
| Olaf Haakonsson | Olav IV of Norway |
| Olaf I | Olaf I |
| Olaf I Głód | Olaf I of Denmark |
| Olaf I Tryggvason | Olaf I of Norway |
| Olaf II Święty | Olaf II of Norway |
| Olaf III Pokojowy | Olaf III of Norway |
| Olaf Kölzig | Olaf Kölzig |
| Olaf V | Olav V of Norway |
| Olaf V Norweski | Olav V of Norway |
| Olaine | Olaine |
| Olandia | Öland |
| Olanzapina | Olanzapine |
| Olaria Rio de Janeiro | Olaria Atlético Clube |
| Olaus Magnus | Olaus Magnus |
| Olbia | Olbia |
| Olbracht Gasztołd | Albrecht Goštautas |
| Olbrotowiec | Sperm Whale |
| olbrzym | giant |
| olbrzymi | cyclopean |
| olcha | alder |
| Olching | Olching |
| Olchon | Olkhon |
| Old Firm | Old Firm |
| Old Friends From Young Years | Old Friends from Young Years |
| Old Shatterhand | Old Shatterhand |
| Old Trafford | Old Trafford |
| Oldboy | Oldboy |
| Oldenburg | Oldenburg |
| Oldenburgowie | House of Oldenburg |
| Oldham | Oldham |
| Oldoinyo Lengai | Ol Doinyo Lengai |
| Oldrzych | Oldrich of Bohemia |
| Oldsmobile | Oldsmobile |
| Oldřich Duras | Oldřich Duras |
| Oldřich Nejedlý | Oldřich Nejedlý |
| OLE | Object Linking and Embedding |
| Ole Einar Bjørndalen | Ole Einar Bjørndalen |
| Ole Gunnar Solskjær | Ole Gunnar Solskjær |
| Ole Nydahl | Ole Nydahl |
| Ole Rømer | Ole Rømer |
| Ole von Beust | Ole von Beust |
| olecczanka | female resident of Olecko |
| Olecko | Olecko |
| Oleg | Oleg of Novgorod |
| Oleg Antonow | Oleg Antonov |
| Oleg Gordijewski | Oleg Gordievsky |
| Oleg Kaługin | Oleg Kalugin |
| Oleg Kotow | Oleg Kotov |
| Oleg Makarow | Oleg Makarov |
| Oleg Maskajew | Oleg Maskaev |
| Oleg Michał | Oleg I of Chernigov |
| Oleg Mieńszykow | Oleg Menshikov |
| Oleg Mądry | Oleg of Novgorod |
| Oleg Pieńkowski | Oleg Penkovsky |
| Oleg Romancew | Oleg Romantsev |
| Oleg Romaniszyn | Oleg Romanishin |
| Oleg Salenko | Oleg Salenko |
| Oleg Serebrian | Oleg Serebrian |
| Oleg Władimirowicz Łosew | Oleg Losev |
| Oleg Łobow | Oleg Lobov |
| Oleg Światosławowicz | Oleg I of Chernigov |
| Oleg Świętosławowicz | Oleg I of Chernigov |
| Oleguer | Oleguer Presas |
| Oleica fioletowa | Meloid beetle |
| Oleicowate | Blister beetle |
| olej | oil |
| Olej arganowy | Argan oil |
| olej chłodniczy | cooling oil |
| Olej hydrauliczny | Hydraulic fluid |
| Olej jojoba | Jojoba oil |
| olej mineralny | mineral oil |
| Olej napędowy | Diesel |
| olej roślinny | vegetable oil |
| Olej syntetyczny | Synthetic oil |
| Olej z miodli indyjskiej | Neem oil |
| Olej z pestek winogron | Grape seed oil |
| Oleje syntetyczne | Synthetic oil |
| olejek | oil |
| olejek eteryczny | essential oil |
| Olena Zubriłowa | Olena Zubrilova |
| olenek | Olenekian |
| Oleniok | Olenyok River |
| Olesko | Olesko |
| Oleszyce | Oleszyce |
| Oleum | Oleum |
| Olewsk | Olevsk |
| Oleśnica | Oleśnica |
| Olešnice | Olešnice |
| Olga | Olga |
| Olga Aleksandrowna Romanowa | Grand Duchess Olga Alexandrovna of Russia |
| Olga Aleksandrówna Romanowa Kulikowska | Grand Duchess Olga Alexandrovna of Russia |
| Olga Bryzgina | Olga Bryzgina |
| Olga Connolly | Olga Fikotová |
| Olga Fiodorowna | Olga Feodorovna of Baden |
| Olga Gyarmati | Olga Gyarmati |
| Olga Kaniskina | Olga Kaniskina |
| Olga Karnowicz | Olga Valerianovna Paley |
| Olga Kijowska | Olga of Kiev |
| Olga Knipper | Olga Knipper |
| Olga Konstantinowna Romanowa | Olga Konstantinovna of Russia |
| Olga Kotlarowa | Olga Kotlyarova |
| Olga Kuzienkowa | Olga Kuzenkova |
| Olga Morozowa | Olga Morozova |
| Olga Nikołajewna Romanowa | Grand Duchess Olga Nikolaevna of Russia |
| Olga Puczkowa | Olga Poutchkova |
| Olga Pyliewa | Olga Pyleva |
| Olga Riabinkina | Olga Ryabinkina |
| Olga Romanowa | Grand Duchess Olga Nikolaevna of Russia |
| Olga Rubcowa | Olga Rubtsova |
| Olga Sawczuk | Olga Savchuk |
| Olga Zajcewa | Olga Zaitseva |
| Olga Zawiałowa | Olga Zavyalova |
| Olga Żarkowa | Olga Jarkova |
| Olgiate Comasco | Olgiate Comasco |
| Olgierd | Algirdas |
| Olgierd Giedyminowic | Algirdas |
| Olha Kobylańska | Olha Kobylyanska |
| Olhão da Restauração | Olhão |
| Olibriusz | Olybrius |
| Oliena | Oliena |
| oligarchia | oligarchy |
| Oligocen | Oligocene |
| Oligomery | Oligomer |
| Oligonukleotydy | Oligonucleotide |
| oligopol | oligopoly |
| Olimp | Mount Olympus |
| Olimpi Rustavi | FC Olimpi Rustavi |
| Olimpia | Olympia |
| Olimpia Asunción | Olimpia Asunción |
| Olimpia de Gouges | Olympe de Gouges |
| Olimpia Mancini | Olympia Mancini |
| Olimpia Tegucigalpa | Club Deportivo Olimpia |
| Olimpiada Iwanowa | Olimpiada Ivanova |
| Olimpiada Machabejska | Maccabiah Games |
| Olimpiada Specjalna | Special Olympics |
| Olimpiada szachowa | Chess Olympiad |
| Olimpias | Olympias |
| Olimpiejon | Temple of Olympian Zeus |
| Olimpija Lublana | HDD Olimpija Ljubljana |
| Olimpijka | Olimpijka |
| olimpijski | olimpic |
| Olimpijski Konkurs Sztuki i Literatury | Art competitions at the Olympic Games |
| Olimpo Bahía Blanca | Olimpo de Bahía Blanca |
| Olimps Ryga | JFK Olimps Rīga |
| Olinda | Olinda |
| Olinek Okrąglinek | Rolie Polie Olie |
| Olingo | Olingo |
| Olint | Olynthus |
| Olita | Alytus |
| Oliveira de Azeméis | Oliveira de Azeméis |
| Oliveira de Frades | Oliveira de Frades |
| Oliveira do Hospital | Oliveira do Hospital |
| Olivenza | Olivenza |
| Oliver Bierhoff | Oliver Bierhoff |
| Oliver Cromwell | Oliver Cromwell |
| Oliver Heaviside | Oliver Heaviside |
| Oliver Kahn | Oliver Kahn |
| Oliver Neuville | Oliver Neuville |
| Oliver Phelps | James and Oliver Phelps |
| Oliver Riedel | Oliver Riedel |
| Oliver Shanti | Oliver Shanti |
| Oliver Smithies | Oliver Smithies |
| Oliver Stone | Oliver Stone |
| Oliver Tambo | Oliver Tambo |
| Oliver Twist | Oliver Twist |
| Oliver Winchester | Oliver Fisher Winchester |
| Olivera Jevtić | Olivera Jevtić |
| Olivia de Havilland | Olivia de Havilland |
| Olivia Lewis | Olivia Lewis |
| Olivia Lufkin | Olivia Lufkin |
| Olivia Newton-John | Olivia Newton-John |
| Olivier Besancenot | Olivier Besancenot |
| Olivier Gruner | Olivier Gruner |
| Olivier Messiaen | Olivier Messiaen |
| Olivier Panis | Olivier Panis |
| oliwa | oil |
| Oliwa z oliwek | Olive oil |
| Oliwer | Oliver |
| Oliwia | Olivia |
| Oliwin | Olivine |
| Oliwiny | Olivine |
| Oliwić | Oil |
| oliwka | olive |
| Oliwka europejska | Olive |
| Oliwkowate | Oleaceae |
| oliwkowy | olive |
| Oliwnik wąskolistny | Elaeagnus angustifolia |
| Oliwnikowate | Elaeagnaceae |
| Olkusz | Olkusz |
| Ollastra | Ollastra Simaxis |
| Olli Rehn | Olli Rehn |
| Ollie | Ollie |
| Ollon | Ollon |
| Olmedo Riobamba | Centro Deportivo Olmedo |
| Olof Rudbeck starszy | Olaus Rudbeck |
| Olof Skötkonung | Olof Skötkonung |
| Olof Vilhelm Arrhenius | Olof Vilhelm Arrhenius |
