| Oklahoma Bible Academy | Academic & Science |
| Openbare Bibliotheek Amsterdam | Academic & Science |
| Old Bostonian Association | Business |
| Ontario Bar Association | Business |
| Oklahoma Bankers Association | Business |
| Oklahoma Bar Association | Business |
| O'Brien & Associates | Business |
| Oregon Bankers Association | Business |
| Oil Buying Alliance | Business |
| One Bar Association | Business |
| Oregon Business Association | Business |
| Ontario Beekeepers' Association | Business |
| Online Business Account | Business |
| Online Behavioral Advertising | Business |
| Open Business Accounting | Business |
| Outsourcing Bookkeeping Accounting | Business |
| Out of Box Audit | Business |
| Outside Business Activities | Business |
| Office of Business Affairs | Business |
| Oregon Bioscience Association | Community |
| Omaha Bar Association | Community |
| Oklahoma Bandmasters Association | Community |
| Oxford Broadcasting Association | Community |
| Oregon Biomedical Association | Community |
| Ohio Bursars Association | Community |
| Opened Bible Academy | Community |
| Obadiah | Community |
| Optical Booster Amplifier | Computing |
| Office Business Applications | Computing |
| Outlook Backup Assistant | Computing |
| Operations Bridge Analytics | Computing |
| Online Business App | Computing |
| Oracle Business Analytics | Computing |
| Object Behavior Analysis | Electronics |
| Organized Brazilian Activities | General |
| O Breathing Apparatus | General |
| Outward Bound Angeles | General |
| Outstanding Black Achievers | General |
| Outward Bound Adventures | General |
| Optical Brightening Agent | General |
| O2 breathing apparatus | General |
| On Board Audio | General |
| Our Barrel Ale | General |
| Our Better Angels | General |
| On Board Air | General |
| Optical Brightening Agents | General |
| Output-based aid | General |
| Optimized Hydraulic Brakes | General |
| On Board Analysis | General |
| Ohio Bus Association | General |
| Office of Biotechnology Activities | Governmental |
| One Bermuda Alliance | Governmental |
| Oban, Queensland, Australia | Regional |
| Office Business Application | Softwares |
| Oxygen Breathing Apparatus | Space Science |
| Outdoor Basketball Association | Sports |
| On Base Average | Sports |
| Ontario Basketball Association | Sports |
| Orinda Baseball Association | Sports |
| Opponent Batting Average | Sports |
