AO, aO, Ao, or ao may refer to:
Places
Ao (building) Ao, Estonia, village in Väike-Maarja Parish, Lääne-Viru County, Estonia Ao Line, commuter railway line in Hyōgo Prefecture, Japan Ao River (Zhejiang) (鳌江), Zhejiang, China Ao River (Fujian) (敖江), Fujian, China Ao Station, railway station in the city of Ono, Hyōgo Prefecture, Japan Aodu, capital of Shang dynasty, near Zhengzhou Aoshima, Ehime, island in Japan Aoshima, Miyazaki, island in Japan Angola (ISO 3166-1 alpha-2 code AO)
Arts and entertainment Adults Only, an entertainment rating AO Music (AOmusic), a world-music fusion group consisting of Jay Oliver, Miriam Stockley and others Ao: The Last Hunter, a 2010 prehistoric drama film Eureka Seven: AO, Japanese mecha anime television series Lord Ao, a fictional deity in the Dungeons & Dragons universe Annoying Orange, an American comedy web series
Businesses and organizations AO (originally American Optical Company) eyeglass lenses, a brand now merged with Carl Zeiss Vision AO Foundation (originally ), a non-profit organisation dedicated to the treatment of trauma and disorders of the musculoskeletal system AO Racing, an American sports car racing team AO World, a UK retailer of household appliances trading under the brand name ao.com AO, or (), a type of Russian corporate entity; see open joint-stock company Athletics Ontario, formally Ontario Track and Field Association (OTAF) Australian Airlines (IATA code AO) Australian Open, one of the four major tennis tournaments held each year
Government and politics Administrative Office of the United States Courts Administrative Officer (United Kingdom), a grade within the UK's Civil Service Administrative Officer (Hong Kong), a grade within the Hong Kong's Civil Service Autonomous oblast, type of Russian administrative division Autonomous okrug, type of Russian administrative division NSDAP/AO, Foreign Organization branch of the Nazi Party Officer of the Order of Australia, postnominal AO
Military Area of operations, a U.S. military term A US Navy hull classification symbol: Fleet oiler (AO) AO-, the prefix for several firearms Aviation Ordnanceman, a US Navy occupational rating
Philosophy and religion Alpha and Omega (abbreviation) Ao (Māori mythology), a deity in Māori mythology Ao (turtle), a creature in Chinese mythology Ao, a type of Easter Island wood carving
Science and technology (697402) Ao, a main-belt asteroid .ao, top-level Internet domain code for Angola Acridine orange, a fluorescent dye Adaptive optics, an astronomical imaging technology Ambient occlusion, a shading method in computer graphics AMSAT-OSCAR, a satellite naming convention Applied Optics, scientific journal published by the Optical Society of America (OSA) Arctic oscillation, a climate pattern Atomic orbital, in physics and chemistry Ausenium, a misidentified chemical element (atomic symbol "Ao") Authorship obfuscation, a privacy technique
Surnames and initials Ao (surname) (), a Chinese surname Ou (surname) (/ and /), romanized as Ao in Cantonese Ao Omae (born 1992), Japanese fiction writer Aaron Owens (born 1976), American streetball player
Other uses Alphabetically ordered Ao (color) Ao (digraph) Ao Naga, an ethnic group in northeastern India Ao language, a Tibeto-Burman (Sino-Tibetan) language spoken by the Ao Naga Central Naga languages, a Sino-Tibetan language family of India or , meaning extraordinary professor (academic rank in Germany) Australian Open, an annual tennis tournament in Melbourne, Australia A, an abbreviation of "Anno", meaning "In the year" (as in Anno Domini) Te Ao Māori (literally "The Māori world"), Māori cultures and traditions
See also Alpha and Omega (disambiguation)
A0 (disambiguation) Ꜵ, a medieval norse ligature of A and O Å, a letter derived from A with an O above or beside it