- Open Door Ministries
- Open MRI
- Open Pantry Food Mart
- Open Pantry Food Marts
- Opera House
- Opportunities
- Opportunities Unlimited
- Opportunity Center
- Opportunity House
- Optical Boutique
- Optical Center
- Optical Clinic
- Optical Designs
- Optical Express
- Optical Expressions
- Optical Gallery
- Optical Illusions
- Optical Mart
- Optical Options
- Optical Outlet
- Optical Outlets
- Optical Shop
- Optical Shoppe
- Optical World
- Opticare Eye Health & Vision Centers
- Opticare Vision Centers
- Optifast
- Optima
- Optimum Mortgage Services
- Optimum Staffing
- Option One
- Option One Mortgage
- Option One Mortgage Corporation
- Optometric Associates
- Optometric Eye Care Center PA
- Optometric Options
- Optometric Physicians of Washington
- Optometrist
- Oracle Corporation