Dr David Maclagan FRSE (8 February 1785 – 6 June 1865) was a prominent Scottish doctor and military surgeon, serving in the Napoleonic Wars. He served as President of both the Royal College of Physicians of Edinburgh and the Royal College of Surgeons of Edinburgh. He served as Surgeon in Scotland to Queen Victoria.
He was born in Edinburgh on 8 February 1785, the son of Robert MacClaggan (d.1785), surgeon, and Margaret Smeiton, his second wife. His father changed his name to Maclagan some time before David was born, to disassociate himself from various Jacobite connections. David trained as a doctor and surgeon at Edinburgh University, graduating MD in 1805. Too young to join the army as a surgeon, he travelled to London and studied and practiced at St George’s Hospital there. He was admitted into the Royal College of Surgeons in 1807.
In 1809 he served as a military surgeon with the 91st Regiment during the Walcheren Campaign within the Napoleonic Wars. This action saw huge injuries, and Maclagan's experience would have increased exponentially from this experience. From 1810 to 1813 he served in various military campaigns, including the attack on Badajos during the Peninsular War, the Battle of Salamanca, the Battle of Vittoria, the Battle of the Pyrenees, the Battle of Nivelle and the Battle of Nive.
On return to Britain he became a practicing surgeon in Edinburgh in 1815, partly working for the New Town Dispensary on Thistle Street, which he co-founded in that year. In 1823 he lost out to George Ballingall in the choice for Edinburgh University's chair in Military Surgery. He was Consultant surgeon/physician at Edinburgh Royal Infirmary from 1848 until retiral.