- Orthopedic surgeon
- Outdoor furniture store
- Organic restaurant
- Oil store
- Occupational health service
- Office
- Obstetrician-gynecologist
- Open university
- Orthodontist
- Oil field equipment supplier
- Oral surgeon
- Oyster bar restaurant
- Oral and maxillofacial surgeon
- Oxygen equipment supplier
- Orthotics & prosthetics service
- Oncologist
- Otolaryngologist
- Office equipment rental service
- Oriental rug store
- Olive oil bottling company