Batman: The Long Halloween is a 13-issue comic book limited series written by Jeph Loeb with art by Tim Sale. It was originally published by DC Comics in 1996 and 1997. It was inspired by the three Batman: Legends of the Dark Knight Halloween Specials by the same creative team. The entire series has been collected in both trade paperback, and as part of the DC Comics Absolute Editions. The series' success led to Loeb and Sale to reteam for the sequel, Batman: Dark Victory, and Catwoman: When in Rome, which parallels the events in Dark Victory.
Taking place during Batman's early days of crime fighting, The Long Halloween tells the story of a mysterious killer named Holiday, who murders people on holidays, one each month. Working with District Attorney Harvey Dent and Lieutenant James Gordon, Batman races against the calendar as he tries to discover who Holiday is before he claims his next victim each month. The story also ties into the events that transform Harvey Dent into Batman's enemy, Two-Face.
In continuity terms, The Long Halloween continues the story of Batman: Year One. It also revolves around the transition of Batman's rogues gallery from simple mob goons to full-fledged supervillains. It also tells the origin of Two-Face, adding along to the story in Batman: Annual #14.
Jeph Loeb has stated that the genesis of the story was influenced by writer Mark Waid, who, when told that Loeb was working on a story set in the Year One continuity, suggested focusing on Harvey Dent's years prior to becoming Two-Face, as that had not been depicted in depth since the original Year One story.