The Medicinæ Doctor or Doctor of Medicine (M.D. or D.M.) is a doctorate level degree held by medical doctors. See Physician or Medicine for a fuller discussion of the holders of this degree and their field of study.

The M.D. in Canada and the United States is a doctorate level degree. It is a first professional doctorate degree much like the J.D. ( juris doctor ) is. All programs require a previous undergraduate degree or some undergraduate coursework to be completed before acceptance into a medical school. The M.D. typically is earned in 4 years.

In the United States most physicians have earned a M.D., although some may instead hold a D.O.. See the Flexner Report.

In the United Kingdom and in countries that follow its tradition, medical doctors instead graduate as Bachelors of Medicine and Surgery, usually abbreviated as 'MB BS' or 'BM BCh'. The Doctor of Medicine and Master of Surgery are higher doctorates reserved for those who have contributed significantly to the academic study of medicine and surgery respectively. (It follows that the title of "Dr." is technically honorary for the majority of practising physicians in the UK.)

In Finland, physicians hold the degree of Licenciate in Medicine, and as in the UK, the Doctor of Medicine (lääketieteen tohtori) is a higher degree reserved for those who have held a doctoral dissertation.