Spāhbed (; early form spāhpat) is a Middle Persian title meaning "army chief" used chiefly in the Sassanid Empire. Originally there was a single spāhbed, called the Ērān-spāhbed, who functioned as the generalissimo of the Sassanid army. From the time of Khosrau I (r. 531–579) on, the office was split in four, with a spāhbed for each of the cardinal directions. After the Muslim conquest of Persia, the spāhbed of the East managed to retain his authority over the inaccessible mountainous region of Tabaristan on the southern shore of the Caspian Sea, where the title, often in its Islamic form ispahbadh (; Arabic form işbahbadh), survived as a regnal title until the Mongol conquests of the 13th century.