Robert Kinloch Massie III (January 5, 1929 – December 2, 2019) was an American journalist and historian. He devoted much of his career to studying and writing about the House of Romanov, Russia's imperial family from 1613 to 1917. Massie was awarded the 1981 Pulitzer Prize for Biography for Peter the Great: His Life and World. He also received awards for his book Catherine the Great: Portrait of a Woman (2011).

His book Nicholas and Alexandra (1967) was adapted as a British film by the same name that was released in 1971. It starred Laurence Olivier, Michael Jayston, and Janet Suzman.

Born in Versailles, Kentucky, Massie spent much of his youth there and in Nashville, Tennessee. He studied American history at Yale University and modern European history at Oxford University as a Rhodes Scholar. Massie worked as a journalist for Newsweek from 1959 to 1964 and then took a position at the Saturday Evening Post. After he and his family left America for France, Massie wrote and published his breakthrough book, Nicholas and Alexandra, a biography of the last Tsar of Russia, Nicholas II, his wife, Alexandra of Hesse, and their family and cultural/political milieu.