John Clerk, Lord Eldin FRSE FSA was a Scottish judge based in Edinburgh.

John Clerk of Eldin FRSE FSAScot was a Scottish merchant, author, artist, geologist and landowner. The 7th son of Sir John Clerk of Penicuik, Bt, Clerk of Eldin was a figure in the Scottish Enlightenment, best remembered for his influential writings on naval tactics in the Age of Sail. A friend of geologist James Hutton, he was a brother-in-law of architect Robert Adam, and a great-great-uncle of physicist James Clerk Maxwell.