Ralph R. Greenson (born Romeo Samuel Greenschpoon, September 20, 1911 – November 24, 1979) was a prominent American psychiatrist and psychoanalyst. Greenson is famous for being Marilyn Monroe's psychiatrist, and was the basis for Leo Rosten's 1963 novel, Captain Newman, M.D.. The book was later made into a movie starring Gregory Peck as Greenson's character. There has been much conjecture, by investigating officers, press and the public, about Greenson's involvement in a possible cover-up concerning the circumstances of Monroe's death.