Regicide is the purposeful killing of a monarch or sovereign of a polity and is often associated with the usurpation of power. A regicide can also be the person responsible for the killing. The word comes from the Latin roots of regis and cida (cidium), meaning "of monarch" and "killer" respectively.
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. The concept of regicide has also been explored in media and the arts through pieces like Macbeth.