The mad scientist (also mad doctor or mad professor) is a stock character of a scientist who is perceived as "mad, bad and dangerous to know" or "insane" owing to a combination of unusual or unsettling personality traits and the unabashedly ambitious, taboo or hubristic nature of their experiments. As a motif in fiction, the mad scientist may be villainous (evil genius) or antagonistic, benign, or neutral; may be insane, eccentric, or clumsy; and often works with fictional technology or fails to recognise or value common human objections to attempting to play God. Some may have benevolent intentions, even if their actions are dangerous or questionable, which can make them accidental antagonists.
The prototypical fictional mad scientist was Victor Frankenstein, creator of his eponymous monster, who made his first appearance in 1818, in the novel Frankenstein, or the Modern Prometheus by Mary Shelley. Though the novel's title character, Victor Frankenstein, is a sympathetic character, the critical element of conducting experiments that cross "boundaries that ought not to be crossed", heedless of the consequences, is present in Shelley's novel. Frankenstein was trained as both an alchemist and a modern scientist, which makes him the bridge between two eras of an evolving archetype. The book is said to be a precursor of a new genre, science fiction, although as an example of gothic horror it is connected with other antecedents as well.
The year 1896 saw the publication of H. G. Wells's The Island of Doctor Moreau, in which the titular doctor—a controversial vivisectionist—has isolated himself entirely from civilisation in order to continue his experiments in surgically reshaping animals into humanoid forms, heedless of the suffering he causes. In 1925, the novelist Alexander Belyaev introduced mad scientists to the Russian people through the novel Professor Dowell's Head, in which the antagonist performs experimental head transplants on bodies stolen from the morgue, and reanimates the corpses.