Barbara Palmer, 1st Duchess of Cleveland (d. 1709)
Barbara Palmer, 1st Duchess of Cleveland, Countess of Castlemaine (née Barbara Villiers, 27 November [O.S. 17 November] 1640 – 9 October 1709), was an English royal mistress of the Villiers family and perhaps the most notorious of the many mistresses of King Charles II of England, by whom she had five children, all of them acknowledged and subsequently ennobled. Barbara was the subject of many portraits, in particular by court painter Sir Peter Lely.

Barbara's first cousin Elizabeth Villiers (later 1st Countess of Orkney 1657–1733) was the presumed mistress of King William III.