The Gunpowder Plot of 1605, in earlier centuries often called the Gunpowder Treason Plot or the Jesuit Treason, was a failed assassination attempt against King James I of England and VI of Scotland by a group of provincial English Catholics led by Robert Catesby.

The plan was to blow up the House of Lords during the State Opening of England's Parliament on 5 November 1605, as the prelude to a popular revolt in the Midlands during which James's nine-year-old daughter, Princess Elizabeth, was to be installed as the Catholic head of state.

The plot was revealed to the authorities in an anonymous letter sent to William Parker, 4th Baron Monteagle, on 26 October 1605. During a search of the House of Lords at about midnight on 4 November 1605, Fawkes was discovered guarding 36 barrels of gunpowder—enough to reduce the House of Lords to rubble—and arrested.