- Marshfield Medical Center - Eau Claire
- Martin Hospital South
- Martin Luther King Jr. Community Hospital
- Martin Luther King, Jr. Community Hospital
- Martin Medical Center
- Martinsburg VA Medical Center
- Mary & Elizabeth Hospital
- Mary Beth Scialabba
- Mary Breckinridge Appalachian Regional Hospital
- Mary Cadman MT, CCRA
- Mary E Bivins Foundation
- Mary Greeley Medical Center
- Mary Kay
- Mary Lanning Healthcare
- Mary Rutan Hospital
- Mary Starke Harper Geriatric Psychiatry Center
- Mary Washington Hospital
- Maryland Center for Maternal and Child Health
- Maryland Community Health System
- Maryland Department of Business Economic Development
- Maryland Department of Health And Mental Hygiene
- Maryland Department of the Environment
- Maryland Hospital Association
- Maryland Office of Tourism
- Maryland Society of Association Executives
- Marymount Manhattan College
- Marywood University
- Mascaro Construction Co. L.P.
- MasiMax Resources, Inc.
- Masonic Care Community of New York
- Masonic Nursing Home Inc.
- Masonic Retirement Village
- Mass Mutual
- Massachusetts Assistance Centers
- Massachusetts College of Pharmacy and HS
- Massachusetts Convention Center Authority
- Massachusetts Department of Public Health
- Massachusetts Department of Public Health, EMSC
- Massachusetts General Hospital
- Massachusetts League of Community Health Centers, Inc.
- Massena Memorial Hospital
- Massey Escort Service
- MasterCare
- Matagorda County United Way
- Mathematics And Technology Help, Inc.
- Mather Hospital
- Matinair, Inc.
- Matlen Silver Enterprise Solutions
- Matrix Group International Inc.
- Matt Birk and Company