Robert William Liversidge (11 June 1904 – 30 September 1994), formerly Jacob (Jack) Perlsweig, was a British Jewish businessman whose activities sometimes attracted the attention of the police and intelligence services. He was also a reputed spy and the subject of a cause célèbre as an internee in Britain during the Second World War.
Liversidge's parents, Asher Perslweig, a rabbi, and Sarah, were Jewish immigrants to Britain from Russia. He was born in Harringay, London, one of five brothers and three sisters. He left school at the age of 14 and drifted before becoming involved in financial services. In July 1928 two of his associates, David and Dore Baumgart, were tried at the Old Bailey for conspiracy to defraud over share dealings in which Liversidge was also alleged to have been involved. An arrest warrant was issued for him, but it was never executed. He subsequently admitted that he had become involved with some dishonest people, but he always denied being guilty of any wrongdoing.
Some time before 1931 he adopted the name Liversidge (the married name of his eldest sister). In 1931 he applied for a Canadian passport in that name, claiming to have been born in Toronto and misstating his date of birth. He eventually managed a Hollywood recording studio, meeting a minor actress, Wanda Stevenson, and marrying her in 1936.