OA, O.A., Oa, or oa may refer to:
Arts and entertainment Oa (comics), a fictional planet in the DC Comics universe The OA, a television series OpenArena, a video game Opie and Anthony (often "O&A"), a radio show Oriental Adventures, a Dungeons & Dragons sourcebook Orion's Arm, a science fiction project
Businesses and organisations Obavještajna agencija, the Croatian Intelligence Agency Office administration Oficina Anticorrupción, an Argentine law enforcement agency Olympic Air (IATA code OA) Opera Australia, an opera company Opportunitas aequa, a Canadian organization Overeaters Anonymous Oxford Academy (California), a high school Orbital ATK, an aerospace company
People Ma'am OA, nickname of Andrea Veneracion, founder of the Philippine Madrigal Singers Oskar Andersson, Swedish cartoonist who uses the pen name O.A.
Places Oa (Attica), a deme of ancient Attica Ocean Acres, New Jersey, United States Orakzai Agency, Pakistan The Oa, Scotland, United Kingdom Oa (DC Comics), the base of two fictional groups of characters, the Guardians of the Universe and the Green Lantern Corps
Honors Order of Australia, a formal honour Order of the Arrow, the honor society of Scouting America
Science and technology Office automation Oleic acid, a fatty acid Open access, the free online availability of digital content from scholarly sources Operational amplifier, an electronic component Operational analysis, more generally called "operational research", a branch of applied mathematics Osteoarthritis, a disease Length overall (also o/a, o.a. or oa), an abbreviation for overall, used when describing the length of a ship Oxford Archaeology
Other uses Oa (digraph) Obituaries Australia, an online database of obituaries Office Action, a communication from the U.S. Patent and Trademark Office Old Alleynian, an old boy of Dulwich College Old Albanian, an old boy of St Alban School, St Albans Order of Appearance, a synonym for Order of battle Output area, an area of approximately 100 households, derived from the UK Census
See also 0A (disambiguation) OOA (disambiguation)