OFS
- Amiga Old File System
- Free State Province
- OFS (company)
- Object File System
- Office for Students
- Office of Financial Stability
- Oklahoma Office of State Finance
- Old Frisian
- Operation Freedom's Sentinel
- Orange Free State
- Orange Free State (Province)
- Orley Farm School
- Ottawa Fire Service
- Overseas Family School
- Oxford Symposium on Food and Cookery
- Schlumberger Oilfield Services
- Secular Franciscan Order