Mary Ann "Polly" Nichols (née Walker; 26 August 1845 – unknown) was a Whitechapel based prostitute operating in London during the late 1880s. She is well known as the first victim of the infamous Jack the Ripper.
Polly, along with other of Jack the Ripper's five victims, worked in one of the brothels run by Lady O. She shared a room with Nellie, another prostitute. However, during the Whitechapel murders, the Master Assassin Jacob Frye requested her to leave the borough, only for her to be replaced by one of the initiates of the British Brotherhood of Assassins.
She had made passing acquaintance with Detective Frederick Abberline of the Metropolitan Police Service, and so when another woman's body was discovered and publicly thought to be Nichols, Abberline knew otherwise, and revealed as much to Evie Frye at the start of her investigation.