Batman: The Killing Joke is a one-shot superhero comic book written by Alan Moore and drawn by Brian Bolland, published by DC Comics in 1988.

It concerns a largely psychological battle between Batman and his longtime foe The Joker, who intends to drive James Gordon, the Police Commissioner of Gotham City, insane, in order to prove that the most upstanding citizen is capable of going mad. Along the way, flashbacks to The Joker's early life are presented, gradually explaining his origin as a failed stand-up comedian who went insane and became grotesquely disfigured on the same day, never returning to lucidity. The end result could be considered a meditation on the relationship between comedy and madness. Likewise, it could be considered an insight into character, and a person's moral fiber. For example, upon learning that his wife had died and going through a traumatic accident, the Joker went insane. Batman, however, also had what the Joker termed 'a very bad day', but he instead chose to fight for good causes. Jim Gordon went through extreme trauma, but did not lose his sense of self, thus disproving the Joker's theories.

This comic book, although it was a one-shot, had extraordinary impact on the DC universe. Most significant was that Barbara Gordon was shot by the Joker, which put her in a wheelchair and ended her career as Batgirl, and eventually lead to her role as Oracle.

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