Harriet Sarah, Lady Mordaunt (née Moncreiffe; 7 February 1848 – 9 May 1906) was the Scottish wife of an English baronet and member of parliament, Sir Charles Mordaunt. She was the respondent in a sensational divorce case in which the Prince of Wales (later King Edward VII) was embroiled, and after a counter-petition led to a finding of mental disorder she spent the remaining 36 years of her life out of sight in a series of privately rented houses, and then in various private lunatic asylums, finally ending her days in Sutton, Surrey.