- Optician
- Organic farm
- Optometrist
- Occupational therapist
- Optical wholesaler
- Oral surgeon
- Orthodontist
- Office furniture store
- Otolaryngology clinic
- Occupational medical physician
- Obstetrician-gynecologist
- Organic shop
- Office equipment rental service
- Oil & natural gas company
- Otolaryngologist
- Orphanage
- Oil change service
- Oil store
- Off roading area
- Office refurbishment service