The Mad Hatter (Jervis Tetch) is a supervillain appearing in comic books published by DC Comics, commonly as an adversary of the superhero Batman. He is modeled after the Hatter from Lewis Carroll's novel Alice's Adventures in Wonderland, a character often called the "Mad Hatter" in adaptations of Carroll. He is also a scientist who invents and uses technological mind control devices to influence and manipulate the minds of his victims. He is one of Batman's most enduring enemies and belongs to the collective of adversaries that make up Batman's rogues gallery.

The Mad Hatter has been substantially adapted from the comics into various forms of media, including feature films, television series, and video games. He has been voiced by Roddy McDowall in the DC animated universe, Peter MacNicol in the Batman: Arkham video game series, and Griffin Newman in Harley Quinn. He has also been portrayed in live-action by David Wayne in the 1960s Batman series, and Benedict Samuel in the Fox series Gotham. A variation of the character named Liam Crandle appeared in the third season premiere of the Arrowverse series Batwoman, portrayed by Amitai Marmorstein.