The Fallible Fiend is a fantasy novel by American writer L. Sprague de Camp, the third book of his Novarian series. It was first published as a two-part serial in the magazine Fantastic for December 1972 and February 1973, and subsequently expanded and revised for book publication. The novel was first published in book form as a paperback by Signet Books in 1973; it was later reprinted by Remploy (1974), Sphere (1978), Del Rey/Ballantine (1981), Baen (1992) and the Thorndike Press (2002). The Remploy edition was both the first British and first hardcover edition. An e-book edition was published by Gollancz's SF Gateway imprint on September 29, 2011 as part of a general release of de Camp's works in electronic form. It has also been translated into German and Italian.