OOS
- 00s (disambiguation)
- List of ornithological societies
- OO (disambiguation)
- OOS Aviatourist
- Object-oriented scanning
- Occupational overuse syndrome
- Oos (river)
- Oos, Baden-Württemberg
- Origin of Symmetry
- Out Of Sample
- Out of Sight
- Out of Sync (book)
- Out of specification
- OxygenOS
- Scope (project management)
- Stockout