American cousins who were coauthors of a series of more than 35 detective (detective story) novels featuring a character named Ellery Queen.

Dannay and Lee first collaborated on an impulsive entry for a detective-story contest; the success of the result, The Roman Hat Mystery (1929), started Ellery Queen on his career, and after publication of two more mysteries, the cousins were able to become full-time writers. They took turns creating plots and writing stories about the sleuth Queen, giving clues so that readers might solve each case before seeing the answer. Queen's adventures have been adapted for radio, television, and film. The pair also used the pseudonym Barnaby Ross when writing about their second detective creation, Drury Lane, and they would hold debates posing as Queen and Ross, believed by all to be two distinct authors.

Dannay's and Lee's other ventures included Ellery Queen's Mystery Magazine, founded in 1941, which has published some of the best current detective fiction. They also edited numerous anthologies, including 101 Years' Entertainment; Great Detective Stories, 1841–1941 (1945), and cofounded Mystery Writers of America.