Sherlock Holmes is an eccentric detective operating primarily on London, during which his adventures were chronicled in the memoirs of his friend and assistant Dr. John Watson. In May 1891, Holmes confronted Professor James Moriarty, the head of a criminal web that Holmes had been dismantling for some time, at Switzerland's Reichenbach Falls. The two fought and Holmes emerged as the victor after overthrowing Moriarty, who fell to the falls but survived. Afterward, Holmes faked his death, but not without difficulties from Moriarty's right-hand man Colonel Moran.
Since then, Holmes was officially declared deceased to the known public and has since retired as a bee-keeper living in Sussex. It is believed that the only people aware of this were his brother Mycroft Holmes, and more recently Mina Murray and Allan Quatermain. In 1904, Holmes was asked by Murray to consider becoming her League's advisor. However, Holmes declined the offer as he believed that even though the League has good intentions, it and any other "exceptional individuals" often make matters worse for society.
The symbol of the League of Extraordinary Gentlemen appears on his cigarette case, hinting that he was at least once a member the League.
Sherlock Holmes was created by Sir Arthur Conan Doyle and first appeared in A Study in Scarlet and then became the subject of three other novels and nearly sixty short stories. He is often considered one of the most popular fictional characters in history and the standard at which all mystery stories are judged. Moore and O'Neill decided against featuring Holmes as a major character because, as with Dracula, they felt he was such a significant literary character that he would overshadow the rest of the League. The comic is set during the "Great Hiatus", the years in which Holmes faked his death after the events of "The Final Problem", to compensate for Holmes' lack of presence in the series.
The dialogue and action from The League of Extraordinary Gentlemen's depiction of the fight at Reichenbach is imitated very closely by the DC Comics/Wildstorm miniseries Victorian Undead: Sherlock Holmes vs. Zombies, the only substantial difference being Moriarty's transformation into a zombie after the fall.
Though Holmes is not directly mentioned in the League of Extraordinary Gentlemen film, Moriarty briefly alludes to the events of The Final Problem at Reichenbach Falls. He appears in the novelization, in a scene lifted directly from Volume I.