Kithairon (Κιθαιρών, -ῶνος) is a mountain range ("No corner of Kithairon echoless", Oedipus Rex 440) about 10 mi (16 km) long, in central Greece, standing between Boeotia in the north and Attica in the south. It is mainly composed of limestone and rises to 4,623 ft (1,409 m). Its northeast side is formed by the mountain Pastra.
The range was the scene of many events in Greek mythology and was especially sacred to Dionysus. Oedipus was exposed on the mountain, while Aktaion and Pentheus were both dismembered on its slopes. It was also the place where Heracles hunted and killed the Nemean lion, in the first of his long series of heroic deeds.
In historic times, the mountain acted as a backdrop to the Battle of Plataea of 479 BC and was the scene of much skirmishing before the battle itself. In later times fortifications were built both at Plataea and Erythrai as the mountain formed the disputed natural border between Athens and Thebes.
The people of Plataea also personified the mountain as their primal king: "The Plataians know of no king except Asopos and Kithairon before him, holding that the latter gave his name to the mountain, the former to the river". (Pausanias 9.1.1)