The Mad Man is a pornographic novel by Samuel R. Delany, first published in 1994 by Richard Kasak.

In New York in the early 1980s, John Marr, a gay black graduate student, is researching a biography of Timothy Hasler, a philosopher stabbed to death under unexplained circumstances outside a gay bar. As details emerge, Marr finds that his lifestyle is converging with that of Hasler, and he becomes increasingly involved in intense sexual encounters with homeless men, despite his growing awareness of the risks of HIV.

Told in an elegant literary style, The Mad Man is a long (500 pages) and complex novel that Delany describes as a "pornotopic fantasy". As such, it combines a number of perspectives: a realistic portrayal of academic research, New York street life and the pre-HIV gay scene; strongly pornographic portrayals of fellatio, coprophilia, urophilia and mysophilia; magic realism elements such as imaginary genital modification and the bull-like monster that appears in Marr's nightmares; and semi-autobiographical aspects distinctive to Delany's work (the relationship between the intellectual Marr and a street person, Leaky Sowps, mirrors those in many of his previous novels, as well as his real-life partnership with the street person Dennis).