- O&M Investments
- O&M Investments LLC
- Oak Brook Healthcare Centre
- Oak Trace
- Oakridge Gardens Nursing Center
- Oakview
- Obamacare
- Occupancy
- Occupational Safety and Health Administration
- Ocean Healthcare
- Ocean Healthcare Group
- Ochsner Clinic Foundation
- OCR
- Office of Inspector General
- Office of the Actuary
- Ohio Health Care Association
- Ohman Family Living
- OIG
- Olio
- Omega
