It is bordered by the Malian Gulf to the east, Boeotia in the south, Phocis in the south, Aetolia-Acarnania in the southwest, Evrytania in the west, Karditsa regional unit in the north, Larissa regional unit in the north, and Magnesia in the northeast.

Phthiotis covers the northern and southern shorelines of the Malian Gulf, an inlet of the Aegean Sea.

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.

These are (number as in the map in the infobox):[2] The prefecture Phthiotis and Phocis was created in 1845.

[2] Note: Provinces no longer hold any legal status in Greece.