Hugh Hume-Campbell, 3rd Earl of Marchmont PC FRS (15 February 1708 – 10 January 1794), styled Lord Polwarth between 1724 and 1740, was a Scottish politician who sat in the House of Commons from 1734 until 1740 when he succeeded to the peerage as Earl of Marchmont. He sat in the House of Lords as a representative peer from 1750. Marchmont died in January 1794, aged 85, when the earldom became either extinct or dormant. By his first wife he had three daughters and two sons: By his second wife, who died on 12 February 1797, he had no issue.