Search by letter: O
Search by letter
Search by letter: O
- Ocheyedan, Iowa
- Ochiltree County, Texas
- Ochlenberg — Swiss municipality in Oberaargau, Canton of Bern Ochlenberg
- Ōchō (Japanese era, 1311–1312) Ōchō
- Ochre (Ocher): natural earth pigment and its uses Ochre
- Ochsenfurt: historic Main river town in the Würzburg district Ochsenfurt
- Ochtrup (Steinfurt district, North Rhine-Westphalia) Ochtrup
- Ocicat: domestic cat breed with wild-looking spotted coat Ocicat
- Ocimum tenuiflorum (Tulsi) — holy basil plant Ocimum tenuiflorum
- Ockelbo: town and municipal seat in Gävleborg County, Sweden Ockelbo
- Ockelbo Municipality: overview, landscape, history and local life Ockelbo Municipality
- Öckerö — locality in Västra Götaland, Sweden Öckerö
- Öckerö Municipality
- OCLC: Cooperative Library Services and the WorldCat Union Catalog OCLC
- Ocoee, Florida
- Oconee County, South Carolina
- Oconomowoc, Wisconsin
- Oconto County, Wisconsin
- Ocourt — former municipality in the Canton of Jura, Switzerland Ocourt
- Octacílio Pinheiro Guerra
- Octadecagon (18-sided polygon) Octadecagon
- Octagon: definition, properties, history and practical uses Octagon
- Octahedron
- Octal numeral system (base 8) Octal
- Octane (C8H18): chemistry, isomers, fuels, and octane rating Octane
- Octane rating: what it means for gasoline, engines, and fuel performance Octane rating
- Octans — Southern Constellation Marking the South Celestial Pole Octans
- Octave (music): definition, physics, tuning, and musical role Octave
- Octave Mirbeau: French novelist, critic and playwright Octave Mirbeau
- Octavia E. Butler: American Science Fiction Writer and Cultural Influencer Octavia E. Butler
- Octavia Spencer
- Octavio Lepage — Venezuelan politician and brief acting president (1923–2017) Octavio Lepage
- Octavio Paz — Mexican poet, essayist, and Nobel Prize laureate Octavio Paz
- Octene
- Octet: meanings in music, computing, chemistry, and poetry Octet
- Octet rule
- Octobass (octobasse) — the giant orchestral bass Octobass
- October: overview, name, calendar relationships, observances and seasonality October
- October (U2 album) October (album)
- October 1: calendar day, observances, and significance October 1
- October 10
- October 11 — calendar date, observances and notable facts October 11
- October 12
- October 13
- October 14
- October 15
- October 16
- October 17
- October 18
- October 19
- October 2
- October 20 — calendar date, seasonal context, and notable facts October 20
- October 2015 Speaker of the United States House of Representatives election
- October 2018 United States mail bombing attempts
- October 21
- October 22
- October 23
- October 24
- October 25 — calendar date, history and observances October 25
- October 26
- October 27
- October 28
- October 29
- October 3 (calendar date) October 3
- October 30: Calendar Position, Observances, and Notable Events October 30
- October 31 — date overview, cultural observances, and historical notes October 31
- October 4
- October 5
- October 6
- October 7
- October 8
- October 9
- October Revolution (1917): Bolshevik seizure of power in Russia October Revolution
- Octocorallia (Octocorals): soft corals, sea fans and sea pens Octocorallia
- Octopoda — biology, diversity and natural history of octopuses Octopoda
- Octopodiformes
- Octopus: biology, behavior, and relationship with humans Octopus
- Octopus card — Hong Kong contactless stored-value payment card Octopus card
- Octopus's Garden (song by The Beatles) Octopus's Garden
- Octopussy (1983 film) Octopussy
- Oculus — the eye, an architectural opening, and a virtual reality platform Oculus
- Oda Nobunaga (1534–1582): daimyo, reformer, and central figure of the Sengoku era Oda Nobunaga
- Oda of Canterbury
- Odawa (Ottawa): Anishinaabeg people of the Great Lakes region Odawa
- Odawara Castle — history, architecture and visitor guide Odawara Castle
- Odawara, Kanagawa: coastal city and historic gateway Odawara, Kanagawa
- Odd Bondevik (1941–2014) Odd Bondevik
- Odd Future (OFWGKTA) — Los Angeles hip hop collective Odd Future
- Odd Future Records
- Odd Iversen — Norwegian football striker and goalscoring record-holder Odd Iversen
- Odd number
- Odd-toed ungulates (Perissodactyla): anatomy, evolution, and ecology Odd-toed ungulate
- Oddar Meanchey Province, Cambodia Oddar Meanchey province
- Odds
- Ode (poetic form) Ode
- Odebolt, Iowa: A Small Agricultural Community in Western Iowa Odebolt, Iowa
- Oded Fehr
- Odell, Illinois
- Oden — traditional Japanese simmered one-pot dish Oden
- Odense — Denmark's third-largest city and capital of Funen Odense
- Odenwald: low mountain range in Hesse, Bavaria and Baden-Württemberg Odenwald
- Odenwaldkreis
- Oder (Odra) — Central European river Oder
- Oder–Neisse line Oder-Neisse line
- Oder-Spree (district) — Brandenburg, Germany Oder-Spree
- Oderen — commune in Haut‑Rhin, Grand Est, France Oderen
- Odesa: Black Sea port city in southwestern Ukraine Odesa
- Odesa Oblast
- Ödeshög — locality and municipal seat in Östergötland, Sweden Ödeshög
- Ödeshög Municipality, Östergötland County, Sweden Ödeshög Municipality
- Odessa Sathyan (Cheeram Veetti Sathyan) — Indian documentary filmmaker and activist Odessa Sathyan
- Odessa, Texas: Permian Basin city and regional center Odessa, Texas
- Odia Coates (1941–1991) — American singer best known for duet with Paul Anka Odia Coates
- Odia language
- Odilon Redon: French Symbolist painter and master of imaginative media Odilon Redon
- Odin: The Norse All‑Father — roles, myths, symbols, and cultural legacy Odin
- Odinani: The Traditional Religion of the Igbo Odinani
- Odisha: geography, history, culture and society Odisha
- Odo Marquard: German philosopher of pluralism and skepticism Odo Marquard
- Odo of France (Eudes) — King of the West Franks Odo of France
- Odo, Earl of Kent and Bishop of Bayeux Odo, Earl of Kent
- Odoacer — King of Italy and the end of the Western Roman Empire Odoacer
- Odometer (vehicle distance-measuring instrument) Odometer
- Ödön Földessy (1929–2020) — Hungarian Olympic long jumper Ödön Földessy
- Odonata: dragonflies and damselflies Odonata
- Odontoceti: the toothed whales — biology, behaviour, and diversity Odontoceti
- Odontochelys — early toothed turtle with a half-shell (Triassic) Odontochelys
- Odor: chemical basis, perception, history and uses Odor
- Odvar Nordli — Norwegian Labour leader and prime minister Odvar Nordli
- Odysseus — Greek epic hero, king of Ithaca Odysseus
- The Odyssey — Ancient Greek Epic Poem Odyssey
- Óðr: Freyja's Companion in Norse Mythology Óðr
- Organisation for Economic Co-operation and Development (OECD) OECD
- Oecusse (Special Administrative Region of East Timor) Oecusse
- Oedema: causes, types, mechanisms and management Oedema
- Oedipus: legendary king of Thebes and central figure in Greek tragedy Oedipus
- Oegstgeest — municipality in South Holland, Netherlands Oegstgeest
- Ōei — Japanese era name (1394–1428) Ōei
- Oekingen — municipality in the Wasseramt district, canton of Solothurn Oekingen
- Oelixdorf
- Oelwein, Iowa
- Original Equipment Manufacturer (OEM): definition, usage, and distinctions OEM
- Oeneus — King of Calydon and Patron of Winemaking Oeneus
- Oenothera (evening primrose): overview, characteristics, history and uses Oenothera
- Oensingen — municipality in the Gäu district, Canton of Solothurn Oensingen
- Oerlikon (Zürich): district 11 quarter with industrial roots and modern hub Oerlikon (Zürich)
- Oeschebüttel — municipality in Steinburg, Schleswig‑Holstein, Germany Oeschebüttel
- Oeschenbach — municipality in Oberaargau, canton of Bern, Switzerland Oeschenbach
- Oeschgen — municipality in Laufenburg district, Canton Aargau, Switzerland Oeschgen
- Oesling (Éislek): the upland region of northern Luxembourg Oesling
- Oesophagus (esophagus): structure, function, and clinical significance Oesophagus
- Oeste Futebol Clube
- Oestradiol (E2): roles, biology, and clinical significance Oestradiol
- Oestrogen (estrogen): roles, types, production and clinical significance Oestrogen
- Oestrone
- Oestrous cycle
- Oettingen in Bayern — Town in Donau-Ries, Bavaria Oettingen in Bayern
- Oetwil am See: municipality in the Pfannenstiel region of the canton of Zürich Oetwil am See
- Oetwil an der Limmat
- Œuf-en-Ternois — commune in Pas-de-Calais, northern France Œuf-en-Ternois
- Œuilly, Aisne
- Of (English preposition) Of
- Of a Revolution (O.A.R.) — American rock band Of a Revolution
- Of Human Bondage — novel by W. Somerset Maugham and its adaptations Of Human Bondage
- Of Love and Other Demons
- Of Love and Shadows (1994 film) Of Love and Shadows
- Of Mice and Men
- Of Plymouth Plantation — William Bradford’s account of the Pilgrims and Plymouth Colony Of Plymouth Plantation
- Ofanto
- OFC Nations Cup: Oceania's international football championship OFC Nations Cup
- Ofcom — United Kingdom communications regulator Ofcom
- Ofelya Hambardzumyan
- Off the Wall (Michael Jackson album) Off the Wall
- Off‑label use of prescription drugs Off-label use
- Off-road vehicle — design, history, uses, and key features Off-road vehicle
- Off-site data protection (vaulting): overview, methods, and best practices Off-site data protection
- Offa of Mercia (King of Mercia, 757–796) Offa of Mercia
- Offa's Dyke — early medieval earthwork along the England–Wales border Offa's Dyke
- Offal: animal organs, culinary uses and cultural perspectives Offal
- Offekerque — commune in Pas-de-Calais, northern France Offekerque
- Offenbach
- Offenbach Rural District (Landkreis Offenbach) Offenbach (district)
- Offenbach am Main
- Offenburg
- Offensive
- Offensive (military): purpose, types, and historical role Offensive (military)
- Offensive Guard (American and Canadian football) Offensive guard
- Offensive linemen (American football) — roles, positions, and importance Offensive linemen
- Offensive tackle (football) Offensive tackle
- Offering (concept) Offering
- Office Spaces and Roles — Design, Functions, and Modern Hybrid Work Trends Office
- United Nations Office for the Coordination of Humanitarian Affairs (OCHA) Office for the Coordination of Humanitarian Affairs
- Office of Management and Budget
- Office of National Drug Control Policy (ONDCP) Office of National Drug Control Policy
- Office of Public Works (Ireland) Office of Public Works
- Office of Science and Technology Policy (OSTP) — U.S. science policy office Office of Science and Technology Policy
- Office of Strategic Services (OSS) — U.S. World War II Intelligence Agency Office of Strategic Services
- Office of the United States Trade Representative
- Office Space (1999 film) Office Space
- Office suite (software) Office suite
- Officer: roles, ranks, and distinctions in military, police, and organizations Officer
- Officer Candidate School (OCS): Training and commissioning for military officers Officer candidate school
- Officer Creek (Aṉangu Pitjantjatjara Yankunytjatjara Lands) Officer Creek
- Officer of Arms
- Officer railway station (Victoria, Australia) Officer railway station
- Official (holder of an office) Official
- Official language: definition, status, and practical effects Official language
- Official Opposition (Canada)
- Official Opposition (United Kingdom)
- Official Opposition Shadow Cabinet (United Kingdom)
- Official residence
- Official scorer (baseball) Official scorer
- Official U.S. PlayStation Magazine (OPM): history, features and legacy Official U.S. PlayStation Magazine
- Offin (commune in Pas-de-Calais, northern France) Offin
- Offrethun (commune in Pas-de-Calais, northern France) Offrethun
- Offshore investment
- Offside rule (association football) Offside rule
- OFK Beograd
- Öfnerspitze — a rocky summit of the Allgäu Alps Öfnerspitze
- Ofra Haza — Israeli singer and cultural icon Ofra Haza
- Ofrenda — the Día de Muertos altar Ofrenda
- Ofsted: England's Office for Standards in Education, Children's Services and Skills Ofsted
- Ofterschwang — Alpine municipality and ski venue in Oberallgäu, Bavaria Ofterschwang
- Oftringen, canton of Aargau, Switzerland Oftringen
- Ōfunato: coastal city of Iwate Prefecture, Japan Ōfunato
- Oganesson (Og): the synthetic element with atomic number 118 Oganesson
- Ogasawara (Ogasawara Village), Tokyo — the Bonin Islands Ogasawara, Tokyo
- Ogawamachi Station (Tokyo): Toei Shinjuku Line subway station in Chiyoda Ogawamachi Station (Tokyo)
- OGC Nice
- Ogden Dunes, Indiana: coastal town and dune community Ogden Dunes, Indiana
- Ogden Nash: American writer of humorous light verse Ogden Nash
- Ogden R. Reid — U.S. diplomat and congressman Ogden R. Reid
- Ogden, Iowa
- Ogden, Utah: history, geography, and cultural overview Ogden, Utah
- Ogdensburg, New York: River Port and Border City Ogdensburg, New York
- Ogdoad (Egyptian mythology) Ogdoad (Egyptian)
- Ögedei Khan: Second Great Khan of the Mongol Empire Ögedei Khan
- Ogemaw County, Michigan
- Ogenne-Camptort — a commune in Pyrénées-Atlantiques, southwestern France Ogenne-Camptort
- Ogens (Gros-de-Vaud), Vaud, Switzerland Ogens
- Ogeu-les-Bains — commune in Pyrénées-Atlantiques, southwestern France Ogeu-les-Bains
- Ogg — free, open multimedia container format Ogg
- Oggy and the Cockroaches
- Oghi — town in Mansehra District, Khyber Pakhtunkhwa Oghi
- Oghi Tehsil — subdivision of Mansehra District, Khyber Pakhtunkhwa Oghi Tehsil
- Oghuz District (Oğuz) — district of Azerbaijan Oghuz District
- Oglala Lakota County, South Dakota
- Ogle County, Illinois
- Oglesby, Illinois
- Ognes (Aisne) — Commune in northern France Ognes, Aisne
- Ogooué-Ivindo Province (Gabon) Ogooué-Ivindo Province
- Ogooué-Lolo Province
- Ogooué-Maritime Province
- Ogre (mythical creature) Ogre
- Ogre, Latvia: town at the confluence of rivers Ogre, Latvia
- Ogun River (Nigeria) Ogun River
- Ogun State: overview, history, economy and culture Ogun State
- Ogyū Sorai: Tokugawa Confucian Thinker and Reformer Ogyū Sorai
- Oh Brother, Where Art Thou? (The Simpsons episode) Oh Brother, Where Art Thou?
- Oh Se-hoon
- Oh Se-hun (Sehun) — South Korean singer, rapper, dancer, model and actor Oh Se-hun
- Oh! Darling (The Beatles song) Oh! Darling
- Oh! Susanna — Stephen Foster's 1848 minstrel song Oh! Susanna
- Ohangwena Region of Namibia Ohangwena Region
- Ohatchee, Alabama
- Ohey (municipality in Namur, Belgium) Ohey
- Ohio (U.S. state) Ohio
- Ohio County, Indiana
- Ohio County, Kentucky: Overview, Geography, and Community Ohio County, Kentucky
- Ohio County, West Virginia
- Ohio Is for Lovers — debut single by Hawthorne Heights Ohio Is for Lovers
- Ohio Players
- Ohio River: Geography, history, and role in American inland navigation Ohio River
- Ohio State Senate Ohio Senate
- Ohio State University
- Ohio University
- Ohio Valley Conference (OVC) — NCAA Division I collegiate athletic conference Ohio Valley Conference
- Ohio Valley Wrestling (OVW) — Louisville developmental wrestling promotion Ohio Valley Wrestling
- Ohio Wesleyan University
- Ohio, Illinois — small village in Bureau County, USA Ohio, Illinois
- Ohio's 2nd congressional district
- Ohis — small commune in the Aisne department of northern France Ohis
- Yokosuka MXY-7 Ohka (piloted rocket attack aircraft) Ohka
- Ohlone: Indigenous Peoples of the San Francisco and Central California Coast Ohlone
- Ohm (unit of electrical resistance) Ohm
- Ohm's law: relationship between voltage, current and resistance Ohm's law
- Ohmstal (former municipality in Lucerne, Switzerland) Ohmstal
- Ōhō (応保) — Japanese era name, 1161–1163 Ōhō
- Ohsweken Demons — Canadian indoor lacrosse team Ohsweken Demons
- Ohzora — Japanese scientific satellite (launched 14 February 1984) Ohzora
- Oi! — British working‑class punk subgenre Oi!
- Oignies — commune in Pas-de-Calais with mining heritage Oignies
- Oigny-en-Valois: a rural commune in the Aisne department of northern France Oigny-en-Valois
- Oil: types, production, uses and key characteristics Oil
- Oil City, Louisiana
- Oil City, Pennsylvania: history, geography, and legacy of an oil boom town Oil City, Pennsylvania
- Oil field: structure, development, and production Oil field
- Oil lamp: history, design, fuels, and cultural significance Oil lamp
- Oil paint — artist's medium of pigment and drying oil Oil paint
- Oil platform