Professor Moriarty is a fictional character and the arch-nemesis of Sherlock Holmes in the stories written by Sir Arthur Conan Doyle. He is depicted as a brilliant and cunning criminal mastermind who operates in the shadows, orchestrating elaborate schemes and criminal activities.
Professor Moriarty is first mentioned in "The Adventure of the Final Problem," a story in which Sherlock Holmes confronts him in a deadly confrontation at the Reichenbach Falls in Switzerland. Moriarty is described as being a mathematician and a professor, but he uses his genius to lead a criminal network, controlling a vast web of criminals and carrying out elaborate crimes without getting his own hands dirty.
He is portrayed as Holmes' intellectual equal, making him one of the few adversaries who can challenge the detective's deductive abilities and strategic thinking. Moriarty's ultimate goal is to eliminate Sherlock Holmes, viewing him as a formidable obstacle to his criminal enterprises.
While Professor Moriarty only appears directly in one story, he has become one of the most iconic villains in literature. His rivalry with Holmes and their deadly confrontation at the Reichenbach Falls have left a lasting impact on the Sherlock Holmes mythos, and he remains an enduring symbol of cunning and malevolence in the detective's world. Additionally, even though he was intended to be a one-time antagonist, Moriarty's character has been adapted and expanded in numerous works of fiction and various adaptations of the Sherlock Holmes stories.