A Mad Scientist in the Deadlands: Weird West rpg is a character who possesses the Arcane Background: Mad Scientist Edge.

Unlike the other Arcanes in the Weird West, the Mad Scientist Edge is passive in nature. Whereas Hucksters can fling Bolt's O' Doom, Shamans can call down lightning bolts by invoking the spirits of nature and Blessed can heal the injured and give peaceful rest to the Walking Dead, Mad Scientists can't do anything obviously magical at all.

A Mad Scientist has the dubious honor of having attracted the not-so malevolent attention of one or more Manitou, who whisper dark secrets into the mind of their witless ally and provide inspiration for all manner of mystical machinery. Most of the steam-punk technology in Deadlands has its origin in the fevered mind of a Mad Scientist, but the magical energies channeled by the creator during the building of the invention generally make mass production impossible. A variety of Mad Scientists, such as Dr. Hellstromme, have achieved this, which has lead to the wide-spread of Ghost Rock Boilers, Steam Tarantulas, Clockwork Automatons and several of the more exotic (read dangerous)weapons floating around the Weird West.

In the Hell on Earth game, it was Mad Scientist Dr. Hellstromme who created the Ghost Rock Bomb which led to earth's current apocalyptic state.