A guitar armrest designed to relieve the arm stress that a guitarist experiences in the Palmaris Longus muscle caused by the arm resting against the acoustic guitar's lower bout and soundboard side edge. It is made of a one piece injection-molded flexible rubber solid body, with a durometer so as to hold the weight of a guitarist's arm off of the front soundboard so as to prevent scratching and deadening of the sound projected therefrom. Replaceable suction cups extend through the body of the armrest such that their attachment buttons protrude from the armrest's top face and their suction disks protrude from the bottom face. The armrest is temporarily affixed to the lower bout of the guitar by suction means.