James Bonar FRSE (1757–1821) was a Scottish lawyer and amateur astronomer. He served as Solicitor of Excise in Scotland, and was known as a scholar and supporter of learned societies.
The eighth son of John Bonar (1722–1761), minister at Cockpen, Midlothian (and later at Perth) and Christian Currier (d.1771), he was born on 29 September 1757. He was educated at the High School, Edinburgh, and attended Edinburgh University.
Bonar early entered the excise office, but became noted as a scholar. He was a member of the Speculative Society of Edinburgh University, admitted 9 December 1777, and elected an extraordinary member on 24 December 1781, and was for several years treasurer of the Royal Society of Edinburgh. He was one of the original promoters of the Astronomical Institution, and one of the founders of the Edinburgh Subscription Library in 1794.
In 1798 he was elected a Fellow of the Royal Society of Edinburgh and served as its Treasurer from 1798 to 1821.
Bonar died on 25 March 1821.
Bonar was author of the article on "Posts" in the Encyclopædia Britannica of 1794, and the articles on "Alphabet Characters", "Etymology", "Excise", "Hieroglyphics", &c., in the Edinburgh Encyclopædia 1808-18. He wrote also ‘Disquisition on the Origin and Radical Sense of the Greek Prepositions,’ 1804.
Bonar edited the new edition of Ewing's Greek Grammar, and contributed articles to the Edinburgh Magazine, Missionary Magazine, and Scottish Register, 1790–5. He published an English edition of Holbein's Dance of Death, 1788, and wrote the memoir of his brother Archibald Bonar in the second volume of his sermons.