Which story first introduces Professor Moriarty in the Sherlock Holmes canon?

The Final Problem first introduces Professor Moriarty in the Sherlock Holmes canon.

Arthur Conan Doyle published the story in 1893 in The Strand Magazine. Holmes describes Moriarty as a criminal mastermind whose organization stands behind many crimes, making him the detective’s most formidable intellectual opponent.

The story is set largely in Europe, where Holmes attempts to escape Moriarty after uncovering the professor’s criminal network. Their confrontation culminates at the Reichenbach Falls in Switzerland, a location that became central to Holmes mythology.

Readers sometimes assume Moriarty appears earlier because later stories refer to him as an established enemy. The Valley of Fear, published later as a novel, gives him a more substantial role, but The Final Problem is his canonical debut. Doyle eventually brought Holmes back in The Empty House.