ONC
- Cinema of Romania
- Digital Chart of the World
- Ocean Networks Canada
- Octanitrocubane
- Office of the National Coordinator for Health Information Technology
- Old North Church
- Old North Church (Sierra Madre, California)
- Olivet Nazarene College
- Oncidium
- Open Network Computing
- Operational Navigation Chart
- Ordinary National Certificate
- Orthopaedic Nurse Certified