Ellery Queen is a pseudonym created in 1929 by American crime fiction writers Frederic Dannay and Manfred Bennington Lee and the name of their main fictional character, a mystery writer in New York City who helps his police inspector father solve baffling murders. Dannay and Lee wrote most of the more than thirty novels and several short story collections in which Ellery Queen appeared as a character, and their books were among the most popular of American mysteries published between 1929 and 1971. In addition to the fiction featuring their eponymous brilliant amateur detective, the two men acted as editors: as Ellery Queen they edited more than thirty anthologies of crime fiction and true crime, and Dannay founded and for many decades edited Ellery Queen's Mystery Magazine, which has been published continuously from 1941 to the present. From 1961, Dannay and Lee also commissioned other authors to write crime thrillers using the Ellery Queen nom de plume, but not featuring Ellery Queen as a character; several juvenile novels were credited to Ellery Queen, Jr. Finally, the prolific duo wrote four mysteries under the pseudonym Barnaby Ross.

Adding another dimension of complexity to their relations, the two men were cousins, each born in Brooklyn, New York, who created the nom de plume Ellery Queen using their professional names. Frederic Dannay was the professional name of Daniel Nathan (October 20, 1905 – September 3, 1982), and Manfred Bennington Lee that of Emanuel Benjamin Lepofsky (January 11, 1905 – April 3, 1971).