Jack the Ripper was an unidentified serial killer active in the impoverished districts in and around Whitechapel in the East End of London in 1888. In both criminal case files and the contemporary journalistic accounts, the killer was called the Whitechapel Murderer and Leather Apron.

Attacks ascribed to Jack the Ripper typically involved female prostitutes who lived and worked in the slums of the East End of London. Their throats were cut prior to abdominal mutilations. The removal of internal organs from at least three of the victims led to proposals that their killer had some anatomical or surgical knowledge. Rumours that the murders were connected intensified in September and October 1888, and numerous letters were received by media outlets and Scotland Yard from individuals purporting to be the murderer. The name "Jack the Ripper" originated in a letter written by an individual claiming to be the murderer that was disseminated in the media. The letter is widely believed to have been a hoax and may have been written by journalists in an attempt to heighten interest in the story and increase their newspapers' circulation. The "From Hell" letter received by George Lusk of the Whitechapel Vigilance Committee came with half of a preserved human kidney, purportedly taken from one of the victims. The public came increasingly to believe in a single serial killer known as "Jack the Ripper", mainly because of both the extraordinarily brutal nature of the murders and media coverage of the crimes.

Extensive newspaper coverage bestowed widespread and enduring international notoriety on the Ripper, and the legend solidified. A police investigation into a series of eleven brutal murders committed in Whitechapel and Spitalfields between 1888 and 1891 was unable to connect all the killings conclusively to the murders of 1888. Five victimsMary Ann Nichols, Annie Chapman, Elizabeth Stride, Catherine Eddowes, and Mary Jane Kellyare known as the "canonical five" and their murders between 31 August and 9 November 1888 are often considered the most likely to be linked. The murders were never solved, and the legends surrounding these crimes became a combination of historical research, folklore, and pseudohistory, capturing public imagination to the present day.

Mary Ann "Polly" Nichols (née Walker; 26 August 1845 – 31 August 1888) was the first canonical victim of the unidentified serial killer known as Jack the Ripper, who is believed to have murdered and mutilated at least five women in the Whitechapel and Spitalfields districts of London from late August to early November 1888.The two previous murders linked to the Whitechapel murderer are unlikely to have been committed by Jack the Ripper, although the murder of Mary Ann Nichols was initially linked to this series, increasing both press and public interest into the criminal activity and general living conditions of the inhabitants of the East End of London.