The Ridolfi plot was a plot in 1571 to assassinate Queen Elizabeth I of England and replace her with Mary, Queen of Scots. The plot was hatched and planned by Roberto Ridolfi, an international banker who was able to travel between Brussels, Rome and Madrid to gather support without attracting too much suspicion.

Thomas Howard, 4th Duke of Norfolk, (10 March 1536 – 2 June 1572) was an English nobleman and politician. Although from a family with strong Catholic leanings, he was raised a Protestant. He was a second cousin of Queen Elizabeth I through her maternal grandmother, and held many high offices during her reign.

Norfolk was the son of the poet, soldier and politician Henry Howard, Earl of Surrey. He commissioned Thomas Tallis, probably in 1567, to compose his renowned motet in forty voice-parts, Spem in alium.

He was executed for his role in the Ridolfi plot.