The Homeric city of Krissa is identified with the prehistoric settlement on the hill of Agios Georgios, south of Chrissos in the prefecture of Phocis. According to Greek mythology, the city was founded by Chrissos, son of Phocos and father of King Strophios, in whose royal court his son Pylades and his friend Orestis spent their childhood.

Archaeological evidence indicates that the settlement was founded in the Middle Helladic period and that it was fortified in the Mycenaean period, when its population increased greatly because of the influx of people from coastal Kirra, who abandoned their city seeking refuge on the acropolis of Agios Georgios. At the end of the Mycenaean period, however, the site was deserted and remained unpopulated until the Byzantine period, when it was re-occupied.

The French School at Athens excavated the hill in 1935 and 1936. Further excavations inside the modern town are carried out by the Tenth Ephorate of Prehistoric and Classical Antiquities.