Jack the Ripper is an alias given to an unidentified serial killer (or killers) active in the largely impoverished Whitechapel area and adjacent districts of London, England in the late 19th century. The name is taken from a letter sent to the Central News Agency by someone claiming to be the murderer.

The victims were women earning income as casual prostitutes. The Ripper murders were perpetrated in public or semi-public places towards the end of the day; the victim's throat was cut, after which the body was mutilated. Some believe that the victims were first strangled in order to silence them and to explain the lack of reported blood at the crime scenes. The removal of internal organs from some victims led some officials at the time of the murders to propose that the killer possessed anatomical or surgical knowledge.

Newspapers, whose circulation had been growing during this era, bestowed widespread and enduring notoriety on the killer owing to the savagery of the attacks and the failure of the police in their attempts to capture the Ripper, sometimes missing the murderer at his crime scenes by mere minutes. Stewart P. Evans & Donald Rumbelow (2006) Jack the Ripper: Scotland Yard Investigates ISBN 0750942282

Due to the lack of a confirmed identity for the killer, the legends surrounding the Ripper murders have become a combination of genuine historical research, conspiracy theory, and folklore. Over the years, many authors, historians, and amateur detectives have proposed theories regarding the identity (or identities) of Jack the Ripper and his victims. This has given rise to the term Ripperologist to describe professionals and amateurs who study and analyze the case. Robin Odell (2006) Ripperology, ISBN 0873388615