OCS
- Carbonyl sulfide
- Corisco International Airport
- Federation of Old Cornwall Societies
- Microsoft Office Communications Server
- OC (disambiguation)
- OCS (TV network)
- OCS Inventory
- Obsessive-compulsive syndrome
- Ocean Colour Scene
- Office of Community Services
- Office of the Chief Scientist (Australia)
- Officer candidate school
- Oklahoma Christian School
- Old Church Slavonic
- Old Cliftonian Society
- On course side
- Online charging system
- Ontario Cannabis Store
- Opelika City Schools
- Open Collaboration Services
- Operational Combat Series
- Oral corticosteroid
- Original Chicken Sandwich
- Original Chip Set
- Outer Continental Shelf
- Overhead contact system
- Senator O'Connor College School
- Thee Oh Sees
- Öcs