Final answer:
In Shakespeare's 'Macbeth', King Duncan names his eldest son Malcolm as his successor.
Step-by-step explanation:
In William Shakespeare's tragedy Macbeth, King Duncan names his eldest son, Malcolm, as his successor. This is explicitly stated in the text when Duncan declares, "We will establish our estate upon Our eldest, Malcolm, whom we name hereafter The Prince of Cumberland."
This moment is significant as it incites Macbeth's ambition to become King, which becomes a central plot point in the play.