Guildenstern is a character from William Shakespeare's play Hamlet. He is a childhood friend of Hamlet and is summoned by King Claudius to spy on him. Guildenstern, along with Rosencrantz, attempts to uncover the reasons behind Hamlet's erratic behavior. In the play, Guildenstern represents themes of loyalty and betrayal. His actions highlight the moral complexities of friendship and the influence of power. The character has also been explored in modern adaptations, such as Tom Stoppard's play Rosencrantz and Guildenstern Are Dead, which delves into the existential dilemmas faced by these minor characters.