AC
- aC – (s) Attocoulomb
- Ac – (s) Actinium
- AC
- (i) Adriamycin-Cyclophosphamide (chemotherapy)
- Air Conditioning
- Aircraftman
- Alternating Current
- Altocumulus
- ante Christum (Latin, "before Christ"; see BC)
- ante cibum (Latin, "before meals")
- (s) Antigua and Barbuda (FIPS 10-4 country code)
- (i) Associazione Calcio (Italian, "football (soccer) club")
- A/C – (i) Air Conditioned/Conditioning – Aircraft
- AC1 – Aircraftman 1st Class
- AC2 – Aircraftman 2nd Class
- ACA
- (i) Airspace Control Authority
- Airspace Co-ordination Area
- A Current Affair
- ACARS – (a) Aircraft Communications Addressing and Reporting System
- ACAS
- (a) Aboriginal Children's Advancement Society
- Advisory, Conciliation and Arbitration Service
- ACB – (i) Asociación de Clubes de Baloncesto (Spanish for "Association of Basketball Clubs")
- ACC
- (i) U.S. Air Combat Command
- Air Component Commander
- Alpine Club of Canada
- Altocumulus castellanus
- Area Control Center
- Atlantic Coast Conference
- Automatic Climate Control
- ACCA
- (i) The Association of Chartered Certified Accountants
- Automatic Cloud Cover Assessment
- ACCAC – (a) Awdurdod Cymwysterau, Cwricwlwm ac Asesu Cymru (Qualifications, Curriculum and Assessment Authority for Wales)
- ACCD – American Coalition of Citizens with Disabilities
- ACCS – (i) Air Communications and Control Squadron
- ACDA – (i) Arms Control & Disarmament Agency
- ACDC
- (i) Alternating Current Direct Current
- the name of an Australian rock music band
- a term for a bisexual person
- A/Cdre – Air Commodore
- ACDT
- (a) Apple Certified Desktop Technician
- (a) Australian Central Daylight Time
- ACE
- (a) Air Combat Emulator (computer game)
- Allied Command Europe
- Armored Combat Earthmover
- Automatic Computing Engine
- ACES
- (a) Aerolíneas Centrales de Colombia (Spanish, "Central Colombian Airlines")
- Auxiliary Campus Enterprises and Services of Alfred State College
- ACF
- (i) Administration for Children and Families
- American Car and Foundry
- American Culinary Federation
- ACHT – (i) Average Call Hold Time
- ACID – (a) Atomicity, Consistency, Isolation, and Durability (in databases)
- ACINT – (p) Acoustic Intelligence
- ACK – (p) Acknowledge (telecommunications; cf. NAK)
- ACL
- (i) Access Control List
- Anterior cruciate ligament; the initialism can also refer to an injury to this ligament.
- Atlantic Coast Line Railroad
- ACLJ – (i) American Center for Law and Justice
- ACLOS – (i) Automatic CLOS (missile control system)
- ACLS – (i) American Council of Learned Societies
- ACLU
- (i) American Civil Liberties Union
- American Communist Lawyers Union (pejorative slang for the above)
- ACM – many, including Association for Computing Machinery; see entry
- ACMC – (i) (U.S.) Assistant Commandant of the Marine Corps
- ACN
- (i) Airborne Communications Node
- Australian Company Number (number issued by the Australian government as registration of a limited liability company)
- ACNA – (i) Anglican Church in North America
- ACO – (i) Airspace Control Order
- ACOBA – (a) Advisory Committee on Business Appointments
- ACOG – (a) American College of Obstetricians and Gynecologists
- ACOM – (p) (U.S.) Atlantic Command
- ACORN – (a) Association of Community Organizations for Reform Now
- ACP
- (i) African, Caribbean and Pacific Group of States
- Air Control Point
- ACR – (i) Advanced Concepts and Requirements
- ACRI – (p) African Crisis Initiative
- ACRT – (i) Advanced Concepts Research Tool simulator
- ACS
- (i) Affiliated Computer Services (NYSE ACS)
- Alaska Communications Service
- American Cancer Society
- American Chemical Society
- Association of Caribbean States
- Australian Computer Society
- ACSC – (i) Army Command and Staff College (various nations)
- ACST – (i) Australian Central Standard Time
- ACST – (i) American Cooperative School of Tunis
- ACT
- (i) Adaptive Control of Thought (cognitive model)
- American College Test (ing Program)
- Australian Capital Territory (also postal symbol)
- ACT UP – (a) AIDS Coalition to Unleash Power
- ACTD – (i) Advanced Concept Technology Demonstration
- ACTF
- (i) (U.S.) Army Constructive Training Federation
- Australian Children's Television Foundation
- ACT-R – (i) ACT-Rational (cognitive model)
- ACT-R/PM – (i) ACT-R/Perceptual-Motor (cognitive model)
- ACTU – (i) Australian Council of Trade Unions
- ACU – (a) American Conservative Union
- ACUF
- (i) BGN Advisory Committee on Undersea Features
- (a) American Conservative Union Foundation
- ACV – (i) Armoured Combat Vehicle
Read more about this topic: List Of Acronyms And Initialisms: A