John Clerk (later Clerk-Maxwell) of Middlebie FRSE (1790–1856) was a Scottish advocate.
He was the son of Captain James Clerk and Janet Irving. He studied Law and qualified as an advocate in 1811.
He inherited the Middlebie estate near Corsock in Galloway from his grandmother Dorothea Clerk-Maxwell upon her death in 1793; his surname changed at this point. He built a new house on the estate which he called Glenlair, a name which later became used for the estate itself.
He was elected a Fellow of the Royal Society of Edinburgh in 1821, his proposer being Sir George Steuart Mackenzie.
In the 1830s he is recorded as living at 14 India Street in Edinburgh's Second New Town, which is where James Clerk-Maxwell was born.
He was the brother of Sir George Clerk of Penicuik, and brother-in-law of James Wedderburn.
He was married to Frances Hodshon Cay, daughter of Robert Hodshon Cay and Elizabeth Liddell. His children included the mathematical physicist James Clerk-Maxwell.
His brother-in-law was John Cay.