James Hamilton, 4th Duke of Hamilton and 1st Duke of Brandon was a Scottish army officer, politician, courtier and diplomat. He was a major investor in the failed Darien scheme, which cost many of Scotland's ruling class their fortunes. He led the Country Party in the Parliament of Scotland and the opposition to the Act of Union in 1707. He died as the result of the Hamilton–Mohun duel in Hyde Park, Westminster, with Charles Mohun, 4th Baron Mohun, over a disputed inheritance.