AO

AO, aO, Ao, or ao may refer to:

Places

 * Ao, or Aodu, capital of Shang dynasty, near Zhengzhou
 * Ao, Estonia, village in Väike-Maarja Parish, Lääne-Viru County, Estonia
 * Ao Line, commuter railway line in Hyōgo Prefecture, Japan
 * Ao River (Fujian) (敖 江, Áo Jiāng) in Fujian, China
 * Ao Station, railway station in the city of Ono, Hyōgo Prefecture, 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 movie
 * 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 Arbeitsgemeinschaft für Osteosynthesefragen), 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
 * Aktsionernoye Obschestvo or Aktsionernoye Obshchestvo (акционерное общество), 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)

Government and politics

 * Administrative Office of the United States Courts
 * Administrative Officer (United Kingdom), a grade within the United Kingdom'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 United States 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

 * .ao, top-level Internet domain code for Angola
 * 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
 * Ao, the atomic symbol for the misidentified chemical element Ausenium.
 * Acridine orange, a fluorescent dye
 * Authorship obfuscation, a privacy technique

Surnames and initials

 * Ao (surname) (敖), a Chinese surname
 * Ou (surname) (区/區 and 欧/歐), romanized as Ao in Cantonese
 * Ao Omae (大前 粟生, Ōmae Ao, born 1992), Japanese fiction writer
 * Aaron Owens (born 1976), American streetball player

Other uses

 * Alphabetically ordered
 * Ao (color)
 * Ao (digraph)
 * Ao languages
 * Ao Naga, an Indian ethnic group
 * ao or außerordentlicher, meaning extraordinary professor (academic rank in Germany)
 * Australian Open, an annual tennis tournament in Melbourne, Australia
 * Ao, an abbreviation of "Anno", meaning "In the year" (as in Anno Domini)
 * Te Ao Māori (literally "The Māori world"), Māori cultures and traditions