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.

The Spencer family is an aristocratic family in the United Kingdom. From the 16th century, its members have held numerous titles, including the dukedom of Marlborough, the earldoms of Sunderland and Spencer, and the Churchill barony. Two prominent members of the family during the 20th century were Sir Winston Churchill and Diana, Princess of Wales.