James Moriarty is a fictional character created by Sir Arthur Conan Doyle. He is best known as the arch-nemesis of Sherlock Holmes, the famous detective. Moriarty is often depicted as a criminal mastermind, orchestrating a vast network of crime while remaining in the shadows. In the stories, Moriarty is highly intelligent and strategic, often outsmarting his opponents. He first appears in "The Final Problem," where he confronts Holmes in a battle of wits. Moriarty's character has since become a symbol of villainy in literature, inspiring numerous adaptations in film, television, and other media.