Athanasios Diakos (Greek: Αθανάσιος Διάκος, before 1958: Άνω Μουσουνίτσα - Ano Mousounitsa) is a small village in the municipal unit of Kallieis, Phocis, Greece. It was named after the Greek national hero Athanasios Diakos. He may have been born there as well, but this is disputed by the village Artotina. The village is situated on the eastern slope of the Vardousia mountains, above the upper valley of the river Mornos, at about 1000 m elevation. In 2001 its population was 307. It is the largest village in the municipal unit. It is 2 km northwest of Mousounitsa, 12 km east of Artotina and 26 km northwest of Amfissa.