| Abbreviation | Definition |
|---|---|
| OCPA | Open Content Platform Association |
| OCPA | Orange County Paralegal Association |
| OCPA | Orange County Psychological Association |
| OCPA | Overseas Chinese Physicists Association |
| OCQA | Ottawa Chow Qigong Association |
| OCW | Oversea Contract Workers |
| ODA | Ohio Dental Association |
| ODBA | Oroville Downtown Business Association |
| ODC | Offshore Data Centre |
| ODI | Organization Development Institute |
| ODMA | Optical Disc Manufacturers Association |
| ODN | Organization Development Network |
| ODR | Oakland Durant Rockridge |
| ODVA | Open DeviceNet Vendors' Association |
| ODZA | One Drop Zendo Association |
| OEA | Oregon Education Association |
| OEQ | Ordre des ergothérapeutes du Québec (Order of Occupational Therapists of Québec, Canada) |
| OFA | Ohio Florists Association |
| OFA | Oxygenated Fuels Association |
| OFFMA | Ontario Farm Fresh Marketing Association |