Professor James Moriarty is a fictional character and criminal mastermind created by Sir Arthur Conan Doyle to be a formidable enemy for the author's fictional detective Sherlock Holmes. He was created primarily as a device by which Doyle could kill Holmes and end the hero's stories. Professor Moriarty first appears in the short story "The Adventure of the Final Problem", first published in The Strand Magazine in December 1893. He also plays a role in the final Sherlock Holmes novel The Valley of Fear, but without a direct appearance. Holmes mentions Moriarty in five other stories: "The Adventure of the Empty House", "The Adventure of the Norwood Builder", "The Adventure of the Missing Three-Quarter", "The Adventure of the Illustrious Client", and "His Last Bow".

Sir Arthur Ignatius Conan Doyle was a British writer and physician. He created the character Sherlock Holmes in 1887 for A Study in Scarlet, the first of four novels and fifty-six short stories about Holmes and Dr. Watson. The Sherlock Holmes stories are milestones in the field of crime fiction.