Phthiotis covers the northern and southern shorelines of the Malian Gulf, an inlet of the Aegean Sea. It stretches inland towards the west along the valley of the river Spercheios. In the south it covers the upper part of the Cephissus valley. There are several mountain ranges in Phthiotis, including the Othrys in the northeast, the Tymfristos in the west, the Vardousia in the southwest, Oeta in the south and the Kallidromo in the southeast.