Agia Efthymia (Greek: Αγία Ευθυμία, [aˈʝa efθiˈmia]) is a village in the regional unit of Phocis, Greece, located on the foothill of Mount Giona, in the district of Parnassida in Central Greece. It is one of the communities which along with Amfissa, the capital of Phocis, form the municipal unit of Amfissa.
The Myonians are also mentioned by Thucydides in his work History of the Peloponnesian War. Eurylochus, the Spartan general, had to pass through the land of the Ozolian Locrians on his road to Naupactus. For this reason and because he also wanted to detach the Amfissians from Athens, Eurylochus sent a herald to Amfissa as long as he had arrived at Delphi. The Amfissians, who were alarmed at the hostility of the Phocians, gave hostages to him and induced the other Locrian cities to do the same; the first of them were their neighbours, the Myonians, who held the most difficult of the passes.