The Gunpowder Plot of 1605, or the Powder Treason, as it is known at the time, is a failed assassination attempt by a group of provincial English Catholics against King James I of England and VI of Scotland.

The plot intends to kill the king, his family, and most of the Protestant aristocracy in a single attack by blowing up the Houses of Parliament during the State Opening on 5 November 1605.

The conspirators have also planned to abduct the royal children, not present in Parliament, and incite a popular revolt in the Midlands.The Gunpowder Plot is one of many unsuccessful assassination attempts against James I, and follows the Main Plot and Bye Plot of 1603.

Some popular historians have put forward a debate about government involvement in the plot.

On November 5 of each year, people in the United Kingdom and other Commonwealth countries and regions will celebrate the failure (or among some groups, the attempt) of the plot on what is known as Guy Fawkes Night, Bonfire Night, Fireworks Night, Cracker Night or Plot Night; although the political meaning of the festival has grown to be very much secondary today.