James I was the monarch on the English throne when the Gunpowder Plot failed in 1605.
James had become king of England in 1603 after succeeding Elizabeth I, while already ruling Scotland as James VI. His accession united the crowns of England and Scotland under one monarch, although the two kingdoms remained separate states with separate parliaments.
The conspirators hoped to kill James during the State Opening of Parliament and replace him with a Catholic ruler. The plot failed when an anonymous letter prompted officials to search the cellars beneath the House of Lords and discover Guy Fawkes with the gunpowder.
James is often called James I of England and James VI of Scotland. That dual numbering is not a contradiction: it reflects his separate titles in the two kingdoms.