Marion Mainwaring (born 1922) is an American writer, translator, and critic.
Mainwaring is best known as the author who completed Edith Wharton's novel The Buccaneers, published in 1993.[1] She earlier assisted R. W. B. Lewis in researching his Pulitzer- and Bancroft-prize-winning 1976 biography of Wharton.[2] A novelist in her own right, she wrote the novel Murder in Pastiche: or Nine Detectives All at Sea (1954), parodying nine famous fictional detectives, and Murder at Midyears (1953). She translated Youth and Age: Three Novellas by Ivan Turgenev and edited The Portrait Game, records of a parlor game played by Turgenev and his friends. Her most recent work is Mysteries of Paris: The Quest for Morton Fullerton (2001), a biography of Wharton's lover.