| Oiketicus abbotii | Oiketicus kirbyi | Oikophobia |
| Oil and Natural Gas Corporation | Oil City, Pennsylvania | Oil Creek, Quận Crawford, Pennsylvania |
| Oil Creek, Quận Venango, Pennsylvania | Oil Trough, Arkansas | Oileáin Árann |
| Oileides | Oileus bifidus | Oileus heros |
| Oileus nonstriatus | Oileus rimator | Oileus sargi |
| Oilinyphia | Oilinyphia peculiaris | Oilton, Texas |
| Oinacu | Oinam | Oingt |
| Oinophila v-flavum | Oinville-Saint-Liphard | Oinville-sous-Auneau |
| Oinville-sur-Montcient | Oiospermum | Oiospermum involucratum |
| Oiozona | Oiozona geometrica | Oiran |
| Oirase, Aomori | Oirata (bướm đêm) | Oiron |
| Oirschot | Oiry | Oise |
| Oisea celinea | Oiselay-et-Grachaux | Oisemont |
| Oishi Nobuyuki | Oisilly | Oisly |
| Oison | Oisseau | Oisseau-le-Petit |
| Oissel | Oissery | Oissy |
| Oisterwijk | Oistus | Oistus cacicus |
| Oistus edmonstoni | Oistus riveti | Oistus sphenosomus |
| Oistus subaeneus | Oistus submetallicus | Oistus suturalis |
| Oisy, Aisne | Oisy, Nièvre | Oisy, Nord |
| Oisy-le-Verger | Oita | Oita (thành phố) |
| Oita Koichi | Oite (tàu khu trục Nhật) (1924) | Oituz |
| Oitz | Oium | Oiwa Go |
| Oiwa Kazuki | Oizé | Oizon |
| Oizumi Kazuya | Oj, svijetla majska zoro | Ojacastro |
| Ojang-dong | Ojén | Ojdula |
| Ojeong-gu | Ojibwa, Wisconsin | Ojin-tenno |
| Ojinaga | Ojiya, Niigata | Ojocaliente |
| Ojoceratops | Ojoraptorsaurus | Ojos Así |
| Ojos del Salado | Ojos Negros | Ojos-Albos |
| Ojuelos de Jalisco | OK | Ok (núi lửa) |
| OK Computer | OK Corral | OK Go |
| Ok Taec-yeon | Ok Taecyeon | Ok-dong |
| Oka Ichinosuke | OKA-38 Aist | Okabe Motonobu |
| Okabena, Minnesota | Okada Katsuya | Okada Keisuke |
| Okada Masaki | Okada Shohei | Okada Takeshi |
| Okada Yoshio | Okada Yukiko | Okalia globosa |
| Okamejei | Okamejei hollandi | Okamira pulchra |
| Okamoto Hideya | Okamoto Hisataka | Okamoto Lynn |
| Okamoto Masahiro | Okamoto Takuya | Okamoto Yuki |
| Okamuraea | Okamuraea brachydictyon | Okamuraea brevipes |
| Okamuraea filipendula | Okamuraea hakoniensis | Okamuraea micrangia |
| Okamuraea plicata | Okan Derici | Okaniwa Yuki |
| Okano Masayuki | Okano Shunichiro | Okapi |
| Okapi BM25 | Okapia | Okapia johnstoni |
| Okara | Okara (quận) | Okara, Pakistan |
| Okarec | Okaw, Quận Shelby, Illinois | Okawville, Illinois |
| Okawville, Quận Washington, Illinois | Okay | Okay Airways |
| Okaya, Nagano | Okayama | Okayama (thành phố) |
| Okayama, Okayama | Okazaki | Okazaki Makoto (cầu thủ bóng đá) |
| Okazaki Ritsuko | Okazaki Ryohei | Okazaki Shinji |
| Okány | Okçaören, Çamoluk | Okçaören, Gölova |
| Okçu, İdil | Okçu, Çumra | Okçu, Beylikova |
| Okçu, Göle | Okçu, Giresun | Okçu, Niğde |
| Okçugöl, Susurluk | Okçuhan, Malazgirt | Okçular, Alaplı |
| Okçular, Araç | Okçular, Çan | Okçular, Çubuk |
| Okçular, Bartın | Okçular, Bergama | Okçular, Bigadiç |
| Okçular, Bolu | Okçular, Bulanık | Okçular, Cide |
| Okçular, Dinar | Okçular, Harmancık | Okçular, Ilgaz |
| Okçular, Karacabey | Okçular, Karakoçan | Okçular, Kaynarca |
| Okçular, Kovancılar | Okçular, Ortaca | Okçular, Pervari |
| Okçular, Vize | Okçularyeri, Bigadiç | Okçulu, Akdağmadeni |
| Okçulu, Perşembe | Okçumehmetli, Boyabat | Okçuoğlu, Arpaçay |
| Okříšky | Okřínek | Okřešice |
| Okřesaneč | OKB | OKB Sukhoi |
| OKB-1 | OKB-23 | Okcheon |
| Okcheon-dong | Okculu, Doğanşar | Okeaninoscia oliveri |
| Okegawa, Saitama | Okehazama | Oketo, Kansas |
| Oketo, Quận Marshall, Kansas | OKG-40 | OKG-40 Iskra |
| Okha | Okha port | Okhaldhunga (huyện) |
| Okhansky (huyện) | Okhinsky (huyện) | Okhotigone |
| Okhotigone sounkyoensis | Okhotsky (huyện) | Okhtar, Syunik |
| Okhtyrka | Okhtyrka (huyện) | Oki Daitō |
| Oki daitō | Oki Electric Industry | Oki Susumu |
| Okikaze (tàu khu trục Nhật) | Okileucauge | Okileucauge hainan |
| Okileucauge nigricauda | Okileucauge sasakii | Okileucauge tanikawai |
| Okileucauge tibet | Okileucauge yinae | Okimune Toshihiko |
| Okinaga Tarashihime no Mikoto | Okinami (tàu khu trục Nhật) | Okinawa |
| Okinawa (đảo) | Okinawa (định hướng) | Okinawa (tỉnh) |
| Okinawa (thành phố) | Okino Masaki | Okino Tori-shima |
| Okinoerabujima | Okinoshima | Okinotorishima |
| Okinsky (huyện) | Okita Sōji | Okita Soji |
| Okita Souji | Oklahoma | Oklahoma City |
| Oklahoma City, OK | Oklahoma City, Oklahoma | Oklahoma, Pennsylvania |
| Oklalı, Çatalca | Oklalı, Lüleburgaz | Oklavalı, Eleşkirt |
| Oklee, Minnesota | Oklubalı, İnönü | Okluca, Bilecik |
| Okluk, Araç | Okluk, Daday | Okna |
| Okni NO.II | Okny (huyện) | OKO |
| Okoř | Okoboji, Iowa | Okoboji, Quận Dickinson, Iowa |
| Okolona, Arkansas | Okolona, Mississippi | Okolpania captiosa |
| Okolpania favorabilis | Okolpania observabilis | Okondo |
| Okonek | Okoneshnikovsky (huyện) | Okorág |
| Okorvölgy | Okounov | OKR |
| Okroshka | Okrouhlá | Okrouhlá Radouň |
| Okrouhlá, Česká Lípa | Okrouhlá, Cheb | Okrouhlá, Písek |
| Okrouhlička | Okrouhlice | Okrouhlo |
| Okryu (cầu) | Okryu-gwan | Okryukwan |
| Oksana Fyodorova | Oksu-dong | Oktavio Philipp von Boehn |
| Oktoberfest | Oktyabr | Oktyabrsk (huyện) |
| Oktyabrsky (huyện của Amur) | Oktyabrsky (huyện của Bashkortostan) | Oktyabrsky (huyện của Chelyabinsk) |
