Barbara Palmer, 1st Duchess of Cleveland, Countess of Castlemaine, 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.

Villiers is an aristocratic family in the United Kingdom. Over time, various members of the Villiers family were made knights, baronets, and peers. Peerages held by the Villiers family include the dukedoms of Buckingham (1623–1687) and Cleveland (1670–1709), as well as the earldoms of Anglesey (1623–1661), Jersey, and Clarendon. Perhaps the most prominent members of the family were those who received the two dukedoms: George Villiers, 1st Duke of Buckingham (1592–1628) rose to fame and influence as favourite of King James I of England, while Barbara Villiers, Duchess of Cleveland (1640–1709) became a mistress of King Charles II of England, by whom she had five children.