prominent intriguer in England during the early reign of Queen Elizabeth I.

Lady Margaret Douglas was the daughter of Archibald Douglas, 6th Earl of Angus, and Margaret Tudor (daughter of King Henry VII of England and widow of King James IV of Scotland), and in 1544 she married Matthew Stewart (1516–71), 4th Earl of Lennox. Because of her nearness to the English crown, Lady Margaret Douglas was brought up chiefly at the English court in close association with Princess Mary (afterward Queen Mary I), who remained her fast friend throughout life.

On Elizabeth I's accession in 1558 Lady Lennox retired to Yorkshire, where her home at Temple Newsom became a centre for Roman Catholic intrigue. She was determined to secure the succession to both thrones for her family, and by a series of successful maneuvers she married her son Henry Stewart, Lord Darnley, to Mary Stuart, Queen of Scots.

Lady Lennox was sent to the Tower of London in 1566, but after the murder of Darnley in 1567 she was released. She was at first loud in her denunciations of Mary, but was eventually reconciled with her daughter-in-law. Lennox was sent to the Tower again in 1574 because of the marriage of her son Charles, Earl of Lennox, to Elizabeth Cavendish, daughter of the Earl of Shrewsbury, and she was pardoned only after her son's death in 1577. Lady Lennox died the following year, in great poverty, but her life was successful in its main purpose, for her grandson James became King James VI of Scotland and afterward King James I of England.