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.

A rat-catcher is a person who kills or captures rats as a professional form of pest control. Keeping the rat population under control was practiced in Europe to prevent the spread of diseases, most notoriously the Black Death, and to prevent damage to food supplies. In modern developed countries, such a professional is otherwise known as a pest control operative or pest exterminator.