Dr. Terrence Thirteen, known simply as Doctor Thirteen, is a comic book character in the DC Universe.

He is a parapsychologist who investigates reports of supposed supernatural activity with the goal of proving that that allegation is groundless.

Naturally, since he does dwell in the DC Universe, his eventual discovery of actual supernatural beings such as The Spectre and Deadman proved most disconcerting.

Today, his activities are explained that he is unconsciously drawn to supernatural hoaxes and while disproving those, he equally unconsciously ignores the real thing. It was explained by DC's sardonic, down-to-earth mage John Constantine in the mini-series The Books of Magic that since Thirteen does not believe, magic and the supernatural truly do not work for him. In the DC Universe, if you think little of the Tarot, for example, you get nothing out of it; whereas if you do accept its power, it will work for you. (This is akin to the thesis found in such DC titles as Hellblazer and Neil Gaiman's Sandman that everyone makes his or her own Hell or Heaven out of one's own expectations/beliefs/guilt in life.)