Prof David Malcolm Murray Lyon FRSE DPH (1888-1956) was a British physician and medical author. He served as President of the Royal College of Physicians of Edinburgh for the period 1945-47. He was Editor of the Edinburgh Medical Journal.
He was born in Wooler in Northumberland on 12 September 1888. He was the son of William Malcolm Lyon, a veterinary surgeon, and his wife Ebinizer (sic) Campbell. He was educated at George Watson's College then studied Medicine at Edinburgh University, graduating MB ChB in 1910.
In the First World War he served in the Royal Army Medical Corps attached to the Cavalry Field Ambulance and saw action in both Rouen and Mons. After the war he became Assistant physician at Edinburgh Royal Infirmary under Jonathan Meakins, jointly working on insulin research, and being joined by Charles George Lambie from 1922. He received his doctorate (MD) in 1920 and an honorary DSc in 1924. In 1924 he became Professor of Therapeutics at Edinburgh University. In the same year he was elected a Fellow of the Royal Society of Edinburgh. His proposers were James Lorrain Smith, Jonathan Campbell Meakins, James Hartley Ashworth, and George Barger.
From 1936 he was Professor of Clinical Medicine at Edinburgh University.