James Duncan MWS (1804–1861) was a Scottish naturalist. After his education in Edinburgh, he followed the family tradition to work in the Scottish church. He however retired and worked with publishing firms, and among other works helping produce an index of Encyclopaedia Britannica.

He wrote

James Duncan's papers on Diptera appeared in the Magazine of Zoology and Botany ( 1, ii: 145-61; iv: 359-68; v: 453-6)