- Maryland Hospice and Palliative Network
- Maryland University
- Marylanders Against Poverty
- Mass General Brigham
- Mass General Brigham Ventures
- Massachusetts Coalition for Serious Illness Care
- Massachusetts General Hospital
- Massachusetts Medical School Collaborative
- Massachusetts Serious Illness Care Coalition
- Math Venture Partners
- Mathematica
- MatrixCare
- MATTER Chicago
- Maven Equity
- Maxwell Healthcare Associates
- Maxwell Investment Partners
- May Light Hospice
- Mayo Clinic
- Mayo Clinic Hospital
- Mayo Clinic Survey Research Center