- Optometrist
- Optical wholesaler
- Orchid grower
- Occupational medical physician
- Obstetrician-gynecologist
- Optical products manufacturer
- Ophthalmology clinic
- Orchid farm
- Ophthalmologist
- Orthoptist
- Oriental medicine clinic
- Oriental medical clinic
- Otolaryngology clinic
- Orthopedic clinic
- Orthopedic surgeon
- Otolaryngologist
- Organic restaurant
- Organic farm
- Office services
- Outdoor activity organiser