- Manchester Manor Health Care Center
- ManorCare
- Marcum LLP
- Marcus & Milichap
- Marcus & Millichap
- Margaritaville Holdings
- Margolis Center for Health Policy
- Mariner Health Care Inc.
- Maritime Center for Rehabilitation and Nursing
- MarketWatch
- Marquette University
- Marquis
- Marquis Companies
- Marquis Health Consulting Services
- Marquis Health Services
- Marquis Limited
- Marquis LLC
- Marriott
- Marsh
- Marsh McLennan