- Oak Hill Capital Partners
- Oak Hill Partners
- Oak Street Health
- Oasis Hospice & Palliative Care
- Obvious Ventures
- OCA Ventures
- Occupational Safety and Health Administration
- Ochsner Health System
- Odyssey Hospice
- Ohana Health Plan
- Ohio Department of Aging
- Ohio History Connection
- Ohio Living
- Ohio State University
- Ohio’s Hospice
- Ohio’s Hospice LifeCare
- Ohio’s Hospice of Dayton
- Ohio’s Community Mercy Hospice
- Ohio’s Hospice at United Church Homes
- Ohio's Hospice