- Otolaryngologist
- Oil field equipment supplier
- Ophthalmology clinic
- Optical wholesaler
- Optician
- Optical products manufacturer
- Office equipment supplier
- Occupational health service
- Occupational therapist
- Osteopath
- Oldsmobile dealer
- Office furniture store
- Organic drug store
- Office space rental agency
- Outdoor furniture store
- Oil store
- Otolaryngology clinic
- Organic shop
- Orthopedic shoe store
- Outerwear store