Olivia E. Coolidge was born in London, England, a daughter of Sir Robert Ensor, a journalist and historian, and his wife Helen Fisher. She grew up at the family home near High Wycombe in Buckinghamshire. She earned a degree in Classics and Philosophy at Oxford University in 1931, and a master's degree in 1940. She taught Greek, Latin, and English in Germany and England before going to the USA, where she taught at schools in Connecticut and Massachusetts. In 1946, she married Archibald C. Coolidge, also an educator. She made her literary debut with The Greek Myths in 1949, and continued to write for young adults for several decades. She published a total of 27 books, mainly biographies and historical fiction. Other works included The Trojan War (1952); Legends of the North (1951); Makers of the Red Revolution (1963); Men of Athens; Lives of Famous Romans (1965); and biographies of Eugene O'Neill, Winston Churchill, Edith Wharton, Gandhi, and Tom Paine.