Caroline Spencer, Duchess of Marlborough, formerly Lady Caroline Russell, was the wife of George Spencer, 4th Duke of Marlborough.

George Spencer, 4th Duke of Marlborough,, styled Marquess of Blandford until 1758, was a British courtier, nobleman, and politician from the Spencer family. He served as Lord Chamberlain between 1762 and 1763 and as Lord Privy Seal between 1763 and 1765. He is the great-great-great grandfather of Sir Winston Churchill.