AO

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

Places

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

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
AO, 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)
Australian Open, one of the four major tennis tournaments held each year

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

(697402) Ao, a main-belt asteroid
.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

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
Ao languages, a Sino-Tibetan language family of India
ao or außerordentlicher, meaning extraordinary professor (academic rank in Germany)
Australian Open, an annual tennis tournament in Melbourne, Australia
A^o, an abbreviation of "Anno", meaning "In the year" (as in Anno Domini)
Te Ao Māori (literally "The Māori world"), Māori cultures and traditions