| Abbreviation | Definition |
|---|---|
| OB | Ordem dos Bilogos |
| OB | Ordem dos Biólogos |
| OB | Order of Biologists |
| OBBS | Orange Blossom Blues Society |
| OBHS | Ocean Beach Historical Society |
| OBHS | Old Berwick Historical Society |
| OBHS | Ontario Black History Society |
| OBPS | Olave Baden Powell Society |
| OBS | Oklahoma Bicycle Society |
| OBTS | Organizational Behavior Teaching Society |
| OCA | Ontario Classical Association |
| OCDS | Oxford Classical Drama Society |
| OCEANS | Oceans Changing Environments Arts and Nearshore Societies |
| OCG | Austrian Computer Society |
| OCG | Österreichische Computer Gesellschaft |
| OCG | sterreichische Computer Gesellschaft |
| OCHS | Ontario Country Historical Society |
| OCNS | Offsetters Climate Neutral Society |
| OCOS | Orange County Optometric Society |
| OCOS | Orange County Orchid Society |