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

The plan was to blow up the House of Lords during the State Opening of 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. Catesby may have embarked on the scheme after hopes of securing greater religious tolerance under King James had faded, leaving many English Catholics disappointed. His fellow plotters were John Wright, Thomas Wintour, Thomas Percy, Guy Fawkes, Robert Keyes, Thomas Bates, Robert Wintour, Christopher Wright, John Grant, Sir Ambrose Rookwood, Sir Everard Digby and Francis Tresham. Fawkes, who had 10 years of military experience fighting in the Spanish Netherlands in suppression of the Dutch Revolt, was given charge of the explosives.

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. Most of the conspirators fled from London as they learned of the plot's discovery, trying to enlist support along the way. Several made a stand against the pursuing Sheriff of Worcester and his men at Holbeche House; in the ensuing battle Catesby was one of those shot and killed. At their trial on 27 January 1606, eight of the survivors, including Fawkes, were convicted and sentenced to be hanged, drawn and quartered.

Details of the assassination attempt were allegedly known by the principal Jesuit of England, Father Henry Garnet. Although Garnet was convicted and sentenced to death, doubt has since been cast on how much he really knew of the plot. As its existence was revealed to him through confession, Garnet was prevented from informing the authorities by the absolute confidentiality of the confessional. Although anti-Catholic legislation was introduced soon after the plot's discovery, many important and loyal Catholics retained high office during King James I's reign. The thwarting of the Gunpowder Plot was commemorated for many years afterwards by special sermons and other public events such as the ringing of church bells, which have evolved into the Bonfire Night of today. Happy 5th of November