Harvard Medical School (HMS) is the medical school of Harvard University and is located in the Longwood Medical Area in Boston, Massachusetts. Founded in 1782, HMS is the third oldest medical school in the United States. It provides patient care, medical education, and research training through its 15 clinical affiliates and research institutes, including Massachusetts General Hospital (MGH), Boston Children's Hospital, Dana–Farber Cancer Institute, Brigham and Women's Hospital, Beth Israel Deaconess Medical Center, Mount Auburn Hospital, McLean Hospital, Cambridge Health Alliance, The Baker Center for Children and Families, Spaulding Rehabilitation Hospital, and others.

Harvard Medical School also partners with newer entities such as Harvard Catalyst, Broad Institute of MIT and Harvard, Harvard Stem Cell Institute, the Center for Primary Care, and Wyss Institute for Biologically Inspired Engineering.

Harvard Medical School was founded on September 19, 1782, on the initiative of Harvard President Joseph Willard. The founding faculty were John Warren, Aaron Dexter, and Benjamin Waterhouse. It is the third-oldest medical school in the United States, after the Perelman School of Medicine at the University of Pennsylvania and Columbia University College of Physicians and Surgeons.

Lectures were first held in the basement of Harvard Hall, then in Holden Chapel. Students paid no tuition but purchased tickets to five or six daily lectures. The first two students graduated in 1788.

In the following century, the school moved locations several times due to changing clinical relationships, a function of the fact that Harvard Medical School does not directly own or operate a teaching hospital. In 1810, the school moved to Boston at what is now downtown Washington Street. In 1816, the school was moved to Mason Street and was called the Massachusetts Medical College of Harvard University in recognition of a gift from the Great and General Court of Massachusetts. In 1847, the school was moved to Grove Street to be closer to Massachusetts General Hospital. In 1883, the school was relocated to Copley Square. Before this move, Charles William Eliot became Harvard's president in 1869, and found the medical school in the worst condition of any part of the university. He instituted drastic reforms that raised admissions standards, instituted a formal degree program, and defined HMS as a professional school within Harvard University that laid the groundwork for its transformation into one of the leading medical schools in the world.

In 1906, the school moved to its present location in the Longwood Medical and Academic Area.

Harvard Medical School postdoctoral trainees and faculty have been associated with several important medical and public health innovations:

In mid-1847, professor Walter Channing's proposal that women be admitted to lectures and examinations was rejected by the President and Fellows of Harvard College. That year Harriot Hunt became the first woman to apply to Harvard Medical School. Dr. Oliver Wendell Holmes Sr. had recently been made Dean of the school and initially considered accepting her application. He was heavily criticized by the all-male student body as well as the university overseers and other faculty members, and she was asked to withdraw her application. Shortly after Elizabeth Blackwell's graduation from Geneva College in 1849, Hunt applied to Harvard again, but was denied.