Ellery Queen is both a fictional character and a pseudonym used by two American cousins from Brooklyn, New York: Daniel (David) Nathan, alias Frederic Dannay (October 20, 1905–September 3, 1982) and Manford (Emanuel) Lepofsky, alias Manfred Bennington Lee (January 11, 1905–April 3, 1971), to write detective fiction. In a successful series of novels that covered forty-two years, Ellery Queen served as both author's name and that of the detective-hero. Movies, radio shows, and television shows have been based on their works. The two, particularly Dannay, were also responsible for co-founding and directing Ellery Queen's Mystery Magazine, generally considered as one of the most influential English crime fiction magazines of the last sixty-five years. They were also prominent historians in the field, editing numerous collections and anthologies of short stories such as The Misadventures of Sherlock Holmes. Their 994-page anthology for The Modern Library, 101 Years' Entertainment: The Great Detective Stories, 1841-1941, was a landmark work that remained in print for many years. Under their collective pseudonym, the cousins were given the Grand Master Award for achievements in the field of the mystery story by the Mystery Writers of America in 1961.

""How actually did they do it? Did they sit together and hammer the stuff out word by word? Did one write the dialogue and the other the narration? ... What eventually happened was that Fred Dannay, in principle, produced the plots, the clues and what would have to be deduced from them as well as the outlines of the characters and Manfred Lee clothed it all in words. But it is unlikely to have been as clear cut as that." Keating, H.R.F., The Bedside Companion to Crime. New York: Mysterious Press, 1989. ISBN 0-89296-416-2

The cousins also wrote four novels about a detective named Drury Lane using the pseudonym Barnaby Ross, and allowed the Ellery Queen name to be used as a house name for a number of novels written by other authors. (See Ellery Queen (house name).)

"As an anthologist, Ellery Queen is without peer, his taste unequalled. As a bibliographer and a collector of the detective short story, Queen is, again, an historical personage. Indeed, Ellery Queen clearly is, after Poe, the most important American of mystery fiction."