Joseph John-Michael Ellis III (born July 18, 1943) is an American historian whose work focuses on the lives and times of the Founding Fathers of the United States.

His scholarly work has concentrated on the Founding Fathers of the United States, including biographies of John Adams, Thomas Jefferson, and George Washington, the American Revolution, and the history of the Federalist Era, which lasted from 1788 to 1800.

Ellis served as dean of faculty at Mount Holyoke College in South Hadley, Massachusetts from 1980 to 1990; following that, he was named by the trustees to the endowed Ford Foundation Chair in history.

He emphasized how important privacy was to him, and how the president and statesman preferred to work behind the scenes in politics, through letters, meetings and discussions over dinners.

In relation to one of the major questions about his private life, whether Jefferson had a liaison with his slave Sally Hemings, Ellis suggested that evidence was "inconclusive."

This means that for those who demand an answer the only recourse is plausible conjecture, prefaced as it must be with profuse statements about the flimsy and wholly circumstantial character of the evidence.

[9] In June 2001, The Boston Globe revealed that Ellis had misled his students in lectures and the media about his role in the Vietnam War years.

In one of his lectures, Ellis stated that he had been involved in helping to clear an area near My Lai shortly before a well-known massacre was carried out in the village.

In a 2000 interview, he claimed to have been a platoon leader, a paratrooper in the 101st Airborne Division, and to have served on the staff of General William Westmoreland in Saigon.

[17] He cited rumors at Mount Holyoke campus that he had served in Vietnam but would not talk about it because of some disturbing experience as something that led him to fabricate claims of service.