| Mainehealth Franklin Hospital | Farmington, ME | Critical Access Hospitals | 3 stars |
| Mainehealth Maine Medical Center | Portland, ME | Acute Care Hospitals | 4 stars |
| Mainehealth Mid Coast Hospital | Brunswick, ME | Acute Care Hospitals | 3 stars |
| Mainehealth Pen Bay Hospital | Rockport, ME | Acute Care Hospitals | 3 stars |
| Mainehealth Stephens Hospital | Norway, ME | Critical Access Hospitals | 4 stars |
| Mainehealth Waldo Hospital | Belfast, ME | Critical Access Hospitals | 3 stars |
| Manati Medical Center Dr Otero Lopez | Manati, PR | Acute Care Hospitals | 1 star |
| Manning Regional Healthcare Center | Manning, IA | Critical Access Hospitals | Not rated |
| Maple Grove Hospital | Maple Grove, MN | Acute Care Hospitals | 5 stars |
| Marcum and Wallace Memorial Hospital | Irvine, KY | Critical Access Hospitals | 4 stars |
| Margaret Mary Community Hospital Inc | Batesville, IN | Critical Access Hospitals | Not rated |
| Margaretville Memorial Hospital | Margaretville, NY | Critical Access Hospitals | Not rated |
| Mariners Hospital | Tavernier, FL | Critical Access Hospitals | 5 stars |
| Marion General Hospital | Marion, IN | Acute Care Hospitals | 3 stars |
| Marion General Hospital | Marion, OH | Acute Care Hospitals | 4 stars |
| Marion Regional Medical Center | Hamilton, AL | Acute Care Hospitals | 3 stars |
| Marlborough Hospital | Marlborough, MA | Acute Care Hospitals | 2 stars |
| Marlette Regional Hospital | Marlette, MI | Critical Access Hospitals | Not rated |
| Marshall Browning Hospital | Du Quoin, IL | Critical Access Hospitals | Not rated |
| Marshall County Healthcare Center - CAH | Britton, SD | Critical Access Hospitals | Not rated |
| Marshall Medical Center | Placerville, CA | Acute Care Hospitals | 4 stars |
| Marshfield Medical Center - Beaver Dam (Mmc-Bd) | Beaver Dam, WI | Acute Care Hospitals | 2 stars |
| Marshfield Medical Center - Eau Claire | Eau Claire, WI | Acute Care Hospitals | 3 stars |
| Marshfield Medical Center - Minocqua | Minocqua, WI | Acute Care Hospitals | 5 stars |
| Marshfield Medical Center - Neillsville | Neillsville, WI | Critical Access Hospitals | Not rated |
| Marshfield Medical Center - Rice Lake | Rice Lake, WI | Acute Care Hospitals | 2 stars |
| Marshfield Medical Center - Weston | Weston, WI | Acute Care Hospitals | 3 stars |
| Martha's Vineyard Hospital Inc | Oak Bluffs, MA | Critical Access Hospitals | 4 stars |
| Martin Luther King, Jr. Community Hospital | Los Angeles, CA | Acute Care Hospitals | 4 stars |
| Mary Breckinridge ARH Hospital | Hyden, KY | Critical Access Hospitals | Not rated |
| Mary Hitchcock Memorial Hospital | Lebanon, NH | Acute Care Hospitals | 3 stars |
| Mary Immaculate Hospital | Newport News, VA | Acute Care Hospitals | 4 stars |
| Mary Rutan Hospital | Bellefontaine, OH | Acute Care Hospitals | 4 stars |
| Mary Washington Hospital | Fredericksburg, VA | Acute Care Hospitals | 3 stars |
| Marymount Hospital | Garfield Heights, OH | Acute Care Hospitals | 5 stars |
| Masonicare Health Center | Wallingford, CT | Psychiatric | Not rated |
| Massachusetts Eye and Ear Infirmary - | Boston, MA | Acute Care Hospitals | Not rated |
| Massachusetts General Hospital | Boston, MA | Acute Care Hospitals | 5 stars |
| Mayo Clinic | Jacksonville, FL | Acute Care Hospitals | 5 stars |
| Mayo Clinic Health System - Albert Lea and Austin | Albert Lea, MN | Acute Care Hospitals | 5 stars |
| Mayo Clinic Health System - Cannon Falls | Cannon Falls, MN | Critical Access Hospitals | Not rated |
| Mayo Clinic Health System - Fairmont | Fairmont, MN | Acute Care Hospitals | 5 stars |
| Mayo Clinic Health System - Lake City | Lake City, MN | Critical Access Hospitals | Not rated |
| Mayo Clinic Health System - Mankato | Mankato, MN | Acute Care Hospitals | 5 stars |
| Mayo Clinic Health System - Waseca | Waseca, MN | Critical Access Hospitals | Not rated |
| Mayo Clinic Health System Chippewa Valley | Bloomer, WI | Critical Access Hospitals | 4 stars |
| Mayo Clinic Health System Eau Claire Hospital | Eau Claire, WI | Acute Care Hospitals | 5 stars |
| Mayo Clinic Health System in Red Wing | Red Wing, MN | Acute Care Hospitals | 4 stars |
| Mayo Clinic Health System New Prague | New Prague, MN | Critical Access Hospitals | 2 stars |
| Mayo Clinic Health System St. James | St James, MN | Critical Access Hospitals | Not rated |