ACA
- 7-ACA
- A Current Affair (Australian TV program)
- AC Ajaccio
- AC Arles-Avignon
- ACA International
- ACKA
- Absolute Championship Akhmat
- Academic Cooperation Association
- Acapulco International Airport
- Accessible Canada Act
- Achawa language
- Acrodermatitis chronica atrophicans
- Actors Centre Australia
- Adventure Cycling Association
- Advisory Committee for Aeronautics
- Aero Club of America
- Affordable Care Act
- African Cashew Alliance
- African Cricket Association
- Air Canada
- Aka (disambiguation)
- Allied Commission
- American Cadet Alliance
- American Callers Association
- American Camp Association
- American Canoe Association
- American Champion Aircraft
- American Chess Association
- American Chiropractic Association
- American Choreography Awards
- American Citizens Abroad
- American Coatings Association
- American College of Apothecaries
- American Composers Alliance
- American Correctional Association
- American Council for the Arts
- American Counseling Association
- American Country Awards
- American Cryptogram Association
- American Crystallographic Association
- American Signal Corporation
- Amputee Coalition of America
- Analytica Chimica Acta
- Angel Capital Association
- Anglican Church in America
- Angoon Community Association
- Anterior cerebral artery
- Anti-Communist Action
- Anti-Corruption Agency
- Anti-cardiolipin antibodies
- Anti-centromere antibodies
- Antioch–Pittsburg (Amtrak station)
- Arabic chat alphabet
- Arcade Archives
- Arctic Control Area
- Argentine Cricket Association
- Armed Peasant Association
- Army Comrades Association
- Association of Canadian Archivists
- Astronautics Corporation of America
- Atlantic Coast Airlines
- Australasian Corrosion Association
- Australian Coal Association
- Australian Communications Authority
- Australian Counselling Association
- Australian Cricket Academy
- Australian Cricketers' Association
- Austrian Cockpit Association
- Automobile Club of America
- Automóvil Club Argentino
- Azodicarbonamide
- Blueshirts
- British Aerospace EAP
- Hamster Corporation
- NSC-131
- Neo Geo
- Reverse mathematics
- SNK
- The Atheist Experience