Otto Penzler (born July 8, 1942) is an editor of mystery fiction in the United States, and proprietor of The Mysterious Bookshop in New York City, where he lives.
Penzler, who graduated from the University of Michigan, is the co-author the "Encyclopedia of Mystery and Detection" for which he won an Edgar Award in 1977. He also wrote 101 Greatest Movies of Mystery and Suspense (2000). For The New York Sun, he wrote The Crime Scene, a popular weekly mystery fiction column that ran for five years. He has worked with authors including Elmore Leonard, Nelson DeMille, Joyce Carol Oates, Sue Grafton, Mary Higgins Clark, Stanley Ellin, Robert Crais, Michael Connelly, James Lee Burke and Thomas H. Cook.
He founded The Mysterious Press, a publishing house devoted entirely to mystery and crime fiction, in 1975. Among the authors it published (works published in America for the first time, not reprints) are Eric Ambler, Kingsley Amis, Isaac Asimov, Robert Bloch, James M. Cain, Raymond Chandler, Jerome Charyn, Len Deighton, Stanley Ellin, James Ellroy, Patricia Highsmith, P.D. James, H.R.F. Keating, Peter Lovesey, Ed McBain, Ross Macdonald, Marcia Muller, Ellis Peters, Ruth Rendell, Mickey Spillane, Ross Thomas, Donald E. Westlake and Cornell Woolrich. In the 1980s it was publishing more than 100 books a year and the imprint was affiliated with major publishers in England (Century-Hutchinson-Arrow), Japan (Hayakwa Publishing), Italy (Mondadori) and Sweden (Bra Bocker). The Mysterious Book Club became a division of the Book of the Month Club and Mysterious Audios an imprint with Dove Audio.