In “The Two Gentlemen of Verona,” Valentine’s friend who betrays him is Proteus.
Proteus and Valentine begin the play as close friends, although their personalities differ. Valentine travels to Milan to gain experience at court, while Proteus initially remains in Verona because he loves Julia. Proteus is eventually sent to Milan as well, where he discovers that Valentine is in love with Silvia, the Duke of Milan’s daughter.
Proteus then betrays Valentine by informing the Duke that Valentine plans to elope with Silvia. The revelation causes Valentine’s banishment, allowing Proteus to pursue Silvia himself. His actions also betray Julia, because he abandons his vows to her while trying to win his friend’s beloved.
Proteus is not the same character as Thurio, Silvia’s wealthy but unsuccessful suitor, or Sebastian, the name Julia adopts when disguising herself as a page. The play ends with Proteus repenting, Valentine forgiving him, and Proteus returning to Julia—though modern readers often find the final reconciliation morally troubling.