Ptoion

thumb|200px|alt=The site of the sanctuary of Apollo Ptoios at the western end of mount Ptoion|The site of the sanctuary of Apollo Ptoios at the western end of mount Ptoion

Ptoion (Ancient Greek Ptōïon , also Ptōon / , Modern Greek Ptoo Πτώο or Oros Pelagias Όρος Πελαγίας) is a mountain chain in northeastern Boiotia. It stretches from Akraiphia by the former Lake Copais in the west to the Gulf of Euboea in the east, reaching up to 725 m (Agia Pelagia) in the west and 781 m (Petalás) in the east. The massif is particularly famed for the oracle of Apollo, which was located in the sanctuary of Apollo Ptoios at the western end of the range and was among the most important Greek oracles up to the time of the Persian Wars.