| Acronym | Definition |
|---|
| ACO | Automobile Club de l'Ouest (Le Mans racing governing body) |
| ACO | American Cornhole Organization |
| ACO | Atlantic Classical Orchestra (Fort Pierce, FL) |
| ACO | Alarm Cut Off |
| ACO | Algorithms, Combinatorics and Optimization (academic program) |
| ACO | Authenticated Ciphering Offset |
| ACO | Action Cancer Ontario |
| ACO | Additional Call Offering |
| ACO | Authorized Contracting Officer |
| ACO | Arts Computing Office (University of Waterloo) |
| ACO | Airspace Coordination Order |
| ACO | Association Canadienne des Optométristes (Canadian Association of Optometrists) |
| ACO | Association Canadienne des Orthodontistes (Canadian Association of Orthodontists) |
| ACO | Alternate Contracting Officer (US DoD) |
| ACO | Austin Civic Orchestra (Austin, TX) |
| ACO | Acronym Control Officer |
| ACO | Association of Canadian Orchestras |
| ACO | Authorized Certification Official (National Plant Protection Organization) |
| ACO | Academy of Clinical Oncology (continuing medical education provider) |
| ACO | Air Combat Order |
| ACO | Advance Change Order |
| ACO | Atomic Coordinating Office |
| ACO | Advanced Concepts Office |
| ACO | Alvarez Chamber Orchestra (UK) |
| ACO | Airfield Coordination Officer |
| ACO | Automated Console Operations |
| ACO | Army Cryptologic Operations |
| ACO | Atomic-Cell Orbital |
| ACO | Average Communication Overhead |
| ACO | Associate Contracting Officer |
| ACO | Angolan Community of Ontario (Canada) |
| ACO | Assistant Contracts Officer |
| ACO | Area Compliance Officer |
| ACO | Assistant Commanding Officer |
| ACO | Action Cut-Out (switch) |
| ACO | Administrative Consent Order |
| ACO | Administrative Contract(ing) Office(r) |
| ACO | AMP Communications Outlet |
| ACO | Animal Control Officer |
| ACO | Air Control Officer |
| ACO | Air Control Order |
| ACO | Air Officer Commanding |
| ACO | Air Coordination Order |
| ACO | Aircraft Certification Office (FAA) |
| ACO | Airspace Control Order |
| ACO | Australian Chamber Orchestra (Sydney, Australia) |
| ACO | A Clockwork Orange (movie/book) |
| ACO | Animal Control Operations |
| ACO | Architectural Conservancy of Ontario (Canada) |
| ACO | Association of Commissioned Officers |
| ACO | Administrative Compliance Order |
| ACO | Air Cadet Organisation (UK) |
| ACO | Ant Colony Optimization |
| ACO | Action Catholique Ouvrière (French: Catholic Workers' Action) |
| ACO | Australian College of Optometry (est. 1939) |
| ACO | Anglican Communion Office |
| ACO | American College of Orgonomy |
| ACO | Automatic Cut Off |
| ACO | Access Card Office (DOD) |
| ACO | Access Control Object |
| ACO | Athlétic Club de l'Ondaine (French athletic club) |
| ACO | Alpha Chi Omega |
| ACO | ATOMAL control officer (NATO) |
| ACO | Accountable Care Organization (health care) |
| ACO | Area Central Office (telecom) |
| ACO | Assistant Chief Officer (UK Probation Services) |
| ACO | American Composers Orchestra |
| ACO | Allied Command Operation |
| ACO | Action Chrétienne en Orient (French: Christian Action in the East) |
| ACO | Actual Contacts for Outlook (Microsoft) |