Massachusetts General Hospital (Mass General or MGH) is the original and largest teaching hospital of Harvard Medical School and a biomedical research facility located in the West End neighborhood of Boston, Massachusetts. With 25,000 employees it is one of the world's largest hospitals by number of staff. It is the third oldest general hospital in the United States. With Brigham and Women's Hospital, it is one of the two founding members of Partners HealthCare, the largest healthcare provider in Massachusetts.

Massachusetts General Hospital conducts the largest hospital-based research program in the world, with an annual research budget of more than $900 million. It is currently ranked as the #4 best hospital in the United States by U.S. News & World Report and #6 in the world by Newsweek. In November 2017, The Boston Globe ranked MGH 5th place of top workplaces, of Massachusetts companies with over 1,000 employees; this was up from 6th place in 2016.