ACS
- 2-Amino-3-carboxymuconic semialdehyde
- 3-D Secure
- AC Sparta Prague
- AC Sporting
- ACS International Schools
- ACS-1
- ATA Command Set
- Abdominal compartment syndrome
- Access Control Service
- Acetyl-CoA synthetase
- Achinsk Airport
- Acroá language
- Acs (surname)
- Active Club Scotland
- Acute coronary syndrome
- Administration for Children's Services
- Adobe Creative Suite
- Advanced Camera for Surveys
- Advanced Card Systems
- Advanced Cataract Surgery
- Advanced Composites Solutions
- Advanced Contact Solutions
- Aerial Common Sensor
- Affiliated Computer Services
- Air Cess
- Air cavity system
- Alabaster City Schools
- Alaska Communications System
- Alaska Communications Systems
- Alperton Community School
- Alternate care site
- Alternative compensation system
- American Cancer Society
- American Ceramic Society
- American Cheese Society
- American Chemical Society
- American College of Sofia
- American College of Surgeons
- American Colonization Society
- American Community School at Beirut
- American Community School in Amman
- American Community School of Abu Dhabi
- American Community Schools
- American Community Survey
- American Constitution Society for Law and Policy
- American Cooperative School of La Paz
- American Cooperative School of Tunis
- American Crime Story
- American Cryonics Society
- American CueSports Alliance
- Anglo-Chinese School
- Anglo-Chinese Schools, Malaysia
- Anticenter shell
- Applied Communication Sciences
- Arkansas Correctional School
- Army Combat Shirt
- Associated Colleges of the South
- Association of Caribbean States
- Association of Cricket Statisticians and Historians
- Assumption College School
- Atacama Large Millimeter Array
- Atriocaval shunt
- Attack Characterization System
- Attitude control system
- Audience Council Scotland
- Aurora Christian Schools
- Australian Cinematographers Society
- Australian Computer Society
- Australian Cricket Society
- Australian Customs Service
- Avery Coonley School
- Cavalry Corps (Ireland)
- Grupo ACS
- Lehman Alternative Community School
- List of auxiliaries of the United States Navy
- Network Admission Control
- Raybird-3
- Redfern Aboriginal Children's Services
- Solar sail
- System Center Operations Manager
- Toastmasters International
- Ács