Hamlet Sr. is a character in William Shakespeare's play Hamlet. He is the deceased father of the protagonist, Prince Hamlet, and the former King of Denmark. His ghost appears early in the play, revealing that he was murdered by his brother, Claudius, who then took the throne and married Hamlet's mother, Gertrude. The appearance of Hamlet Sr.'s ghost sets the central conflict of the play in motion, as Prince Hamlet grapples with the task of avenging his father's death. This theme of revenge, along with the exploration of grief and betrayal, drives the narrative and shapes Hamlet's character throughout the story.