Margaret Douglas, Countess of Lennox (8 October 1515 – 7 March 1578) was the daughter of Archibald Douglas, 6th Earl of Angus, and Margaret Tudor, Queen Dowager of Scotland. In her youth she was high in the favour of her uncle, King Henry VIII, but twice incurred the King's anger, first for her unauthorised engagement to Lord Thomas Howard, who died in the Tower of London in 1537 because of his misalliance with her, and again in 1540 for an affair with Thomas Howard's nephew Sir Charles Howard, the brother of Queen consort Catherine Howard. On 6 July 1544, she married Matthew Stuart, 4th Earl of Lennox, one of Scotland's leading noblemen. Her son Henry Stuart, Lord Darnley, married Mary, Queen of Scots and was the father of James VI of Scotland (James I of England).