1,726 articles
Oita Prefecture
Oita Prefecture (大分県, Oita-ken), a prefecture in northeastern Kyushu, Japan, capital Oita City. Known as the "Onsen Prefecture" for Beppu and Yufuin hot springs; population about 1.08 million, declining; record 5.36 million overnight guests in 2025.
Okayama-ken
Okayama-ken (岡山県), Okayama Prefecture, is a prefecture in western Japan's Chugoku region on the Seto Inland Sea, established 18 April 1876, capital Okayama City, about 1.8 million people, known for Korakuen Garden, Kurashiki, and Kojima denim.
Okinawa
Okinawa (沖縄県), Japan's southernmost prefecture of 160 islands, former Ryukyu Kingdom annexed in 1879, reverted from US rule in 1972; hosts about 70% of US military facilities in Japan on 0.6% of its land.
Oklahoma
Oklahoma, the 46th U.S. state (admitted November 16, 1907), was formed by merging Oklahoma Territory and Indian Territory after the 1889 land runs; capital area Oklahoma City, population about 4.1 million.
Olomouc Region
Olomouc Region (Olomoucký kraj, NUTS 3 CZ071) is a Czech region in central and northern Moravia with capital Olomouc, five districts, 631,500 residents, 5,271.58 km², a 104 km Polish border, and an industry-weighted economy.
Olt
Olt (Județul Olt) is a county of southern Romania, on the Danube border with Bulgaria, named after the Olt river and home to the ALRO aluminum plant in Slatina.
Omsk Oblast
Omsk Oblast (Омская область), a Russian oblast in southwest Western Siberia with center Omsk; formed 1934, area 141.1 thousand km², about 1.8 million people, manufacturing and agriculture economy.
Ondo State
Ondo State, the "Sunshine State", is a southwestern Nigerian state created 3 February 1976 with capital Akure, 18 LGAs, Nigeria's top cocoa producer, Africa's largest bitumen deposit (42 billion barrels), and the country's lowest multidimensional poverty rate (27%).
Ontario
Ontario, Canada's most populous province (16.3 million, 39.0% of Canada; GDP $1.25 trillion, 38.4% of national), a 1867 Confederation founder with Toronto as capital, 124-seat legislature, nuclear-heavy electricity grid, and 46 treaties with Indigenous nations.
Opole Voivodeship
Opole Voivodeship (województwo opolskie) is Poland's smallest province by population, created 1 January 1999 with capital Opole; 923.5 thousand residents, industrial-agricultural economy, highest per-capita GHG emissions in Poland.
Oran Province
Oran Province (ولاية وهران, Wilaya d'Oran) is Algeria's wilaya no. 31 in the northwest, capital Oran city; 2,114 km², 26 communes, second commercial port, Arzew oil port, raï music birthplace.
Örebro County
Örebro County (Örebro län), a county in central Sweden with seat Örebro, 12 municipalities, about 308,000 inhabitants (2025), formed from Närke plus parts of Västmanland, Värmland, and Västergötland; governor Lotta Finstorp since 2021.
Orenburg Oblast
Orenburg Oblast (Оренбургская область), a Russian federal subject in the southeast of European Russia on the Southern Urals, capital Orenburg; 124,000 km², 1.82 million people, 1,876 km Kazakhstan border, major gas, oil, and grain producer.
Oriental Mindoro
Oriental Mindoro, eastern half of Mindoro island in MIMAROPA, Philippines; capital Calapan; created 1950 by RA 505; 919,504 people (2024), 4,364.72 sq km, home of the endemic tamaraw and seven Mangyan tribes.
Oryol oblast
Oryol oblast (Орловская область), a Central Federal District subject of Russia formed 27 September 1937, capital Oryol; 24,652 km², about 714,000 people, industrial-agrarian economy, grain leader of the Central Federal District.
Osaka Prefecture (大阪府)
Osaka Prefecture (大阪府, Osaka-fu) is one of Japan's two fu-level prefectures, established May 2, 1868 from the Osaka Court, with about 8.75 million residents and host of Expo 2025 on Yumeshima.
Oslo County
Oslo County (Oslo fylke) is the Norwegian county comprising the capital city of Oslo, unusual in being both a municipality and a county and the most populous county.
Östergötland County
Östergötlands län (county code 05), a county in southeastern Sweden formed in 1634, with 13 municipalities, 472,529 inhabitants (2025), and its two dominant cities Linköping and Norrköping.
Østfold fylke
Østfold fylke, a county in southeastern Norway between the Oslofjord and the Swedish border, restored 1 January 2024 from the split of Viken; 12 municipalities, seat Sarpsborg, about 316,000 inhabitants, largest municipality Fredrikstad.
Ostrobothnia (administrative region)
Ostrobothnia (Österbotten, Pohjanmaa) is a west-coast region of Finland with about 179,500 inhabitants, fourteen municipalities, Vaasa and Jakobstad as main cities, a Swedish-speaking majority, and an energy technology cluster.
Osun State
Osun State, southwestern Nigerian state created 27 August 1991 from Oyo State, capital Osogbo, 30 local government areas, Yoruba cultural heartland with Ile-Ife and the UNESCO-listed Osun-Osogbo Sacred Grove; Governor Ademola Adeleke re-elected in 2026 under Accord.
Ouadaï Region
Ouadaï (Ouaddaï, Dar Wadai) is an eastern Chadian province on the Sudan border, capital Abéché, former heart of the 1611 Wadai Sultanate; about 997,000 people, millet and trade economy, and a major destination of Sudanese refugees since 2023.
Ouargla Province
Ouargla Province is an Algerian wilaya, number 30, in the northeastern Algerian Sahara with its capital at Ouargla; one of Algeria's largest provinces, it depends almost entirely on groundwater.
Ouémé Department
Ouémé Department (Département de l'Ouémé), a department of Benin in the southeast, area 1,281 km², nine communes including Porto-Novo, the national administrative capital; 1,100,404 inhabitants at the 2013 census; named for Benin's longest river.
Ouham
Ouham is a prefecture of the Central African Republic in the northwest, capital Bossangoa, part of Yadé Region, named after the Ouham (Bahr Sara) River, a Chari tributary and key agricultural basin.
Ouham-Pendé Prefecture
Ouham-Pendé is a prefecture of the Central African Republic in the northwest, capital Bozoum, on the Chad and Cameroon borders. Known for the 3R armed group, transhumance, artisanal mining, and the 2022 Lim-Pendé split.
Oum el Bouaghi Province
Oum el Bouaghi Province (ولاية أم البواقي), Algerian wilaya 04 in the northeast high plains, created 12 July 1974 from Constantine; 7,638 km², 674,037 people, capital Oum El Bouaghi, 12 daïras, 29 communes since 1984.
Outaouais
Outaouais, Quebec administrative region 07 on the Ottawa River across from Ottawa; capital Gatineau. 428,751 residents (2025), service-based economy (86.7% tertiary), GDP $19.2B (2023), projected +14.3% growth 2021-2051.
Oyo State
Oyo State, a South-West Nigerian state created 3 February 1976 from the Western State with capital Ibadan, nicknamed the Pace Setter; 33 LGAs, 28,454 km², Yoruba heartland named for the Oyo Empire, governed by Seyi Makinde since 2019.
Pahang (ڤهڠ)
Pahang (ڤهڠ), Pahang Darul Makmur, Malaysia's largest Peninsular state (35,965 km², 11 districts), capital Kuantan; population 1.68 million (2025); former Federated Malay State with RM3.184 billion flood mitigation program.