James Matthews Duncan (April 1826 – 1 September 1890) was a Scottish physician, known as a practitioner of and author on obstetrics.

The fifth child of William Duncan, a merchant, and his wife Isabella Matthews, he was born on 29 April 1826 in Aberdeen.

[1] Duncan spent the winter of 1846–7 in Paris, attending the lectures of Gabriel Andral, Jean Cruveilhier, Mathieu Orfila, and Alfred-Armand-Louis-Marie Velpeau.

He assisted Simpson in his experiments in anaesthetics, and on 4 November 1847 experimentally inhaled chloroform to the point of insensibility.

[1] At the end of 1849, after some months of travel in attendance on the Marquess of Bute, Duncan began practice in Edinburgh, mainly as an obstetrician.

He built up a practice, and in 1861 was made physician to the ward for diseases of women in the Royal Infirmary of Edinburgh.

He was elected Fellow of the Royal Society on 7 June 1883, and in the same year was nominated by the Crown a member of the General Council of Medical Education and Registration.