OAS or Oas may refer to:
Chemistry O-Acetylserine, amino-acid involved in cysteine synthesis
Computers Open-Architecture-System, the main user interface of Wersi musical keyboards OpenAPI Specification (originally Swagger Specification), specification for machine-readable interface files for RESTful Web services Oracle Application Server, software platform
Medicine Open aortic surgery, surgical technique Oral allergy syndrome, food-related allergic reaction in the mouth 2'-5'-oligoadenylate synthase, an enzyme OAS1, OAS2, OAS3, anti-viral enzymes in humans
Organizations Office of Aviation Services, agency of the United States Department of the Interior Ontario Archaeological Society, organization promoting archaeology within the Province of Ontario, Canada Organisation Armée Secrète, French far-right paramilitary group, active during the Algerian War (1954–1962), fighting against Algerian independence Organization of American States, a voluntary continental organization of the Americas Oxford Art Society, society for artists in the city of Oxford, England
Transport Oasis LRT station, Singapore, LRT station abbreviation OAS
Other Ohio Auction School, school for auctioneers in Ohio, U.S. Old Age Security, social security payment available to most Canadians aged 65 or older Option-adjusted spread, the yield-curve spread of a fixed-income security, adjusted for the cost of embedded options Oas, Albay, municipality in the Philippines See also Oaş (disambiguation)