In Shakespeare’s Hamlet, the King of Denmark is Claudius.
Claudius is the play’s principal antagonist and the brother of the recently deceased King Hamlet. He takes the Danish throne after secretly murdering his brother by pouring poison into his ear, then marries Queen Gertrude, the late king’s widow. That makes him both Hamlet’s uncle and, after the marriage, his stepfather.
The Ghost of King Hamlet reveals the murder to Prince Hamlet, setting the revenge plot in motion. Claudius is not simply a remote villain: Shakespeare presents him as politically capable and persuasive, especially when dealing with the threat from Norway and the unrest surrounding Hamlet. His private struggle to pray in Act 3 shows that he understands the seriousness of his crimes, even though he cannot bring himself to surrender the rewards they brought him.
A small theatrical detail is often overlooked: although the character is identified in the cast list as “Claudius, King of Denmark,” the name Claudius is not spoken aloud in the play. He is also fictional, rather than a historical Danish king.