- Mattel
- Matthews Brothers Builders
- Matthews Photography, Inc.
- Maui The Magic Island
- Maui United Way
- Max Yield Cooperative
- Maxim Healthcare Services
- Maximus
- Maximus
- Maximus
- Mayaguez Medical Center
- Mayo Clinic
- Mayo Clinic - Jacksonville
- Mayo Clinic Florida
- Mayo Clinic Health System
- Mayo Clinic Health System in Eau Claire
- Mayo Clinic Health System in Eau Claire-Luther Campus
- Mayo Clinic Hospital
- Mayo Clinic Hospital, Methodist Campus
- Mayo Clinic Rochester Transplant Center
- Mayo Clinic-Saint Marys and Methodist Hospitals
- Mayo Clinical Trial Services
- Mayo Regional Hospital
- Maysville Community College
- Mayview State Hospital
- Mazda North American Operations
- MBIA
- MBM Marketing
- MCA Communications Inc.
- McAlester News-Capital and Democrat
- McAlester Public Library
- McAlester Regional Health Center
- McAllen Heart Hospital
- McAllen Medical Center
- McCandlish Holton, PC
- McCollister's Transportation Group
- McCone County
- McCreary Community College
- McCullough Hyde Memorial Hospital - TriHealth
- McCune Foundation
- McCutchen Friends Home
- McDade-Woodcock, Inc.
- McDonough County United Way
- McDonough District Hospital
- McDowell Appalachian Regional Hospital
- McElroy, Deutsch and Mulvaney
- McFarland-Johnson, Inc.
- McGehee Hospital Incorporated (MDCH)
- McGhee Hospital
- McGuffy Industries Inc.