O'Keeffe, Georgia (1887-1986), American artist.
O'Malley, Austin (1858-1932), American physician and humorist.
O'Rourke, Patrick Jake (1947- ), American writer and humorist.
Onassis, Aristotle Socrates (1906-1975).
Ortega y Gasset, José (1883-1955), Spanish philosopher.
Orwell, George (1903-1950), British writer.
Osler, William, Sir (1849-1919), Canadian physician.
Ott, Melvin Thomas “Mel” (1909-1958), American baseball player.