OSC
- Battle for Dream Island
- C0 and C1 control codes
- Czechoslovak Trade Union Association
- LWIR
- Off-site construction
- Office of Special Counsel
- Ohio Supercomputer Center
- Ontario Science Centre
- Ontario Securities Commission
- Open Sound Control
- Open Source Center
- OpenSUSE Build Service
- Orbital Sciences Corporation
- Order of Saint Clare
- Order to show cause
- Ordo Sanctae Crucis
- Organic solar cell
- Orlando Science Center
- Orson Scott Card
- Orthogonal signal correction
- Osceola (Amtrak station)
- Oscoda–Wurtsmith Airport
- Overseas School of Colombo