- Occupational health service
- Oil depot
- Organic drug store
- Optometrist
- Orphanage
- Oil and gas exploration service
- Office of Vital Records
- Oil refinery
- Office supply
- Opera company
- Oxygen equipment supplier
- Office of a fair trade organization
- Office refurbishment service
- Oriental medicine store
- Offal barbecue restaurant
- Oil field equipment supplier
- Outdoor activity organiser
- Orthopedic surgeon
- Oyster bar restaurant
- Organic restaurant