William Palmer (6 August 1824 – 14 June 1856), also known as the Rugeley Poisoner or the Prince of Poisoners, was an English doctor and murderer. Palmer was convicted for the 1855 murder of his friend John Cook, whom he had poisoned with strychnine. He was also suspected of poisoning several other people including his brother and his mother-in-law, as well as four of his children. Palmer made large sums of money from the deaths of his wife and brother after collecting on life insurance, and by defrauding his wealthy mother.
Palmer was hanged in public the year following his conviction. Charles Dickens called Palmer "the greatest villain that ever stood in the Old Bailey".