The League of Extraordinary Gentlemen is a comic book limited series written by Alan Moore and illustrated by Kevin O'Neill, published under the America's Best Comics imprint of DC Comics. As of 2007 it comprises two six-issue limited series, each collected in graphic novel format, with several new stories coming soon. There is also a prequel short story, "Allan and the Sundered Veil", included in the first series, and an extensive appendix detailing the alternate universe the League is set in, called "The New Traveller's Almanac", in Volume Two. The story takes place in 1898 in a fictional world where all of the characters and events from Victorian literature (and possibly the entirety of fiction) coexist. The world the characters inhabit is one more technologically advanced than our own was in the same era, but also home to the strange and supernatural.

The Victorian setting allowed Moore and O'Neill to insert "in-jokes" and cameos from many works of Victorian fiction, while also making contemporary references and jibes, and also bear numerous steampunk influences. In the first issue, for example, there is a half-finished bridge to link Britain and France, referencing problems constructing the real-world Channel Tunnel (this is also a possible reference to H. G. Wells's novel The War in the Air, which mentions a cross-channel bridge).

The juxtaposition of characters from different sources in the same story is similar to science fiction writer Philip José Farmer's works centering around the Wold Newton family. Besides the character of Campion Bond, who could not be called the ancestor of James Bond directly due to licensing issues, every character in the series, from the dominatrix schoolmistress Rosa Coote to single-panel throwaway characters like Inspector Dick Donovan, is an established character from a previous work of fiction or an ancestor of a character from modern-day fiction. This has lent the series considerable popularity with fans of esoteric Victoriana, who have delighted in attempting to place every character who makes an appearance.

Sherlock Holmes and Dracula are notably absent from the League's adventures due to their deaths prior to the events of the series, though the former has a brother (Mycroft Holmes) in the League and appears in a flashback sequence, and the latter's connections to Wilhelmina Murray do not go unnoticed. Holmes is still believed by the public to be deceased following the events of The Final Problem. Moore has noted that he felt these two seminal characters would overwhelm the rest of the cast. According to The New Traveler's Almanac Mina meets Sherlock Holmes in 1904 as an elderly beekeeper. She also comments that he is "more likeable and warm than Mycroft".