Earl of Loudoun (pronounced "loud-on" /ˈlaʊdən/), named after Loudoun in Ayrshire, is a title in the Peerage of Scotland. It was created in 1633 for John Campbell, 2nd Lord Campbell of Loudoun, along with the subsidiary title Lord Tarrinzean and Mauchline. The 1st Earl's wife Margaret was the granddaughter and heiress of Hugh Campbell, who had been created Lord Campbell of Loudoun; he resigned the peerage in favour of his grandson-in-law, who was later created an earl. The heir apparent to the Earldom uses the courtesy title Lord Mauchline.