Regicide Regicide The broad definition of regicide ( "of king" + ' "killer" or ' "killing") is the deliberate killing of a monarch, or the person responsible for the killing of a person of royalty. In the British tradition, it refers to the judicial execution of a king after a trial, reflecting the historical precedent of the trial and execution of Charles I of England. More broadly, it can also refer to the killing of an emperor or any other reigning sovereign. Before the Tudor period, English kings had been murdered while imprisoned (for example Edward II or Edward V) or
Regicide killed in battle by their subjects (for example Richard III), but none of these deaths are usually referred to as regicide. The word regicide seems to have come into popular use among foreign Catholics when Pope Sixtus V renewed the papal bull of excommunication against the "crowned regicide" Queen Elizabeth I, for—among other things—executing Mary, Queen of Scots, in 1587. Elizabeth had originally been excommunicated by Pope Pius V, in "Regnans in Excelsis", for converting England to Protestantism after the reign of Mary I of England. The defeat of the Spanish Armada and the "Protestant Wind" convinced most English people