- Marthas Vineyard Hospital
- Martin County Hospital
- Mary Breckinridge ARH Hospital
- Mary Free Bed Rehabilitation at Covenant Healthcare
- Mary Free Bed Rehabilitation Hospital
- Mary Greeley Medical Center
- Maryland Heights Center for Behavioral Health
- Mary Lanning Memorial Hospital
- Marymount Hospital
- Mary Rutan Hospital
- Mary Starke Harper Geriatric Psychiatry Center
- Mary Washington Hospital
- Mason District Hospital
- Mason Health
- Masonicare Health Center
- Massachusetts Eye and Ear
- Massachusetts General Hospital
- Massac Memorial Hospital
- Massena Hospital
- MassGeneral Hospital for Children
- Matagorda Regional Medical Center
- Matheny Medical and Educational Center
- Mather Hospital
- Mat-Su Regional Medical Center
- Maui Memorial Medical Center
- Maury Regional Medical Center
- Mayaguez Medical Center
- Mayers Memorial Hospital
- Mayhill Hospital
- Maynard Childrens Hospital at ECU Health Medical Center