Ellery Queen is a crime fiction pseudonym created in 1929 by Frederic Dannay and Manfred Bennington Lee, and later used by other authors under Dannay and Lee's supervision. Dannay and Lee's main fictional character, whom they also named Ellery Queen, is a mystery writer in New York City who helps his police inspector father solve baffling murders. Most of the more than thirty novels and several short story collections in which Ellery Queen appeared as a character were written by Dannay and Lee, and were among the most popular American mysteries published between 1929 and 1971. From 1961, Dannay and Lee also commissioned other authors to write crime thrillers under the Ellery Queen authorial name, but not featuring Ellery Queen as a character.

Daniel Nathan, professionally known as Frederic Dannay (b Brooklyn October 20, 1905 – d New York September 3, 1982), and Emanuel Benjamin Lepofsky, professionally known as Manfred Bennington Lee (b Brooklyn January 11, 1905 – d Roxbury, Connecticut April 3, 1971), were American cousins from Brooklyn, New York. In addition to writing most of the novels and short stories featuring the brilliant amateur detective Ellery Queen, Dannay and Lee edited more than thirty anthologies of crime fiction and true crime, which were also published under the Ellery Queen pseudonym. Dannay was the founder and longtime editor of Ellery Queen's Mystery Magazine, which has been published continuously from 1941 to the present.

Dannay and Lee also wrote four mysteries under the pseudonym Barnaby Ross, a name that they later allowed another author to use. Several juvenile novels were credited to Ellery Queen, Jr.