John Barclay FRSE FRCPE FRCSE FLS MWS (10 December 1758 – 21 August 1826) was an eminent Scottish comparative anatomist, extramural teacher in anatomy, and director of the Highland Society of Scotland.
He was born in Cairn, Perthshire 10 December 1758, the son of a farmer, and nephew of John Barclay, who established the Berean Church.
He was educated at Muthill parish school.
Barclay initially studied divinity at the University of St Andrews, and served as a minister. Then working as a family tutor, he educated himself in biological topics and anatomy. Pupils of his entered the University of Edinburgh in 1789, and Barclay became an assistant there to John Bell the anatomist, and was also associated with his brother Charles Bell. His employer Sir James Campbell financed the completion of his medical course.
Barclay qualified M.D. at Edinburgh, before studying anatomy under Andrew Marshall for a year in London. He returned to Edinburgh and established himself as an anatomical lecturer in 1797. Until 1825 he delivered two complete courses of human anatomy, a morning and an evening one, every winter session, and for several years before his death gave a summer course on comparative anatomy. His classes gradually grew in reputation; in 1804 he was formally recognised as a lecturer on anatomy and surgery by the Edinburgh College of Surgeons, and in 1806 he became a fellow of the Edinburgh College of Physicians.