Lyon Sprague de Camp (27 November 1907 – 6 November 2000), usually referred to as L. Sprague de Camp and who sometimes wrote under the pseudonym Lyman R. Lyon, was an American writer. He wrote science fiction, fantasy, and biographical works, particularly of genre authors; he is the author of Lovecraft: A Biography (Doubleday, 1975).
Although he did not coin the term, de Camp is credited with the first usage of "extraterrestrial" as a noun with the meaning of "alien life," and with coining the abbreviation "E.T." He did so in the first part of his two-part article "Design for Life", which was published in May 1939 in Astounding Science Fiction magazine.
De Camp worked for many years editing and writing fiction in continuation of Robert E. Howard's Conan cycle. He edited a series of anthology publications through the 1960s that renewed and maintained interest in high fantasy and sword and sorcery stories, old and new. His editorial work also spread the works to new audiences. He also worked editorially and wrote with Lin Carter.