The Ratcatcher is a character appearing in American comic books and other media published by DC Comics, primarily as an enemy of Batman. He belongs to the collective of adversaries that make up the Dark Knight's rogues gallery. Once an actual rat-catcher in Gotham City, Flannegan sank into a life of crime. Calling himself the Ratcatcher because of his special ability to communicate with and train rats, Flannegan has used his minions to plague Gotham on more than one occasion by unleashing hordes of the vermin.

The DC Extended Universe (DCEU) is an American media franchise and shared universe centered on superhero films and other series starring various titular superheroes produced by DC Films / DC Studios, distributed by Warner Bros. Pictures, and based on characters that appear in American comic books published by DC Comics. Despite numerous film series in the past on characters such as Superman, Batman, and Green Lantern, none of those film series were connected. The DCEU debuted in 2013 with Man of Steel, centered on Superman, and has grown to include other characters such as Batman, Wonder Woman, and several others included in this list. The shared universe, much like the original DC Universe in comic books, was established by crossing over common plot elements, settings, cast, and characters, and crossed over with separate timelines from other DC-licensed film series in The Flash to create a "multiverse" before being largely rebooted as the new DC Universe franchise under new management from DC Studios.