Francis Tresham (c. 1567 – 1605) was one of the English provincial Catholics who planned the failed Gunpowder Plot of 1605, a conspiracy to assassinate King James I. Having previously been imprisoned for his role in a failed rebellion and involved in missions to Spain that sought support for persecuted English Catholics, Tresham joined the Gunpowder Plot in October 1605. Its leader Robert Catesby asked him to provide a large sum of money and the use of Rushton Hall, but Tresham apparently provided neither, instead giving a small amount of money to fellow plotter Thomas Wintour. Tresham also expressed his concern that two of his brothers-in-law would be killed if the plot succeeded. An anonymous letter delivered to one of them was handed to Robert Cecil, 1st Earl of Salisbury, and was decisive in foiling the conspiracy. Historians suspect that Tresham wrote it, although this is unproven.