William Palmer (6 August 1824 – 14 June 1856), also known as the Rugeley Poisoner or the Prince of Poisoners, was an English doctor found guilty of murder in one of the most notorious cases of the 19th century. He was convicted for the 1855 murder of his friend John Cook, and was executed in public by hanging the following year. He had poisoned Cook with strychnine, and was suspected of poisoning several other people including his brother and his mother-in-law, as well as four of his children who died of "convulsions" before their first birthdays. 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 out of thousands of pounds, all of which he lost through gambling on horses.