Amphictyon (/æmˈfɪkti.ɒn/; Ancient Greek: Ἀμφικτυών), in Greek mythology, was the second son of Deucalion and Pyrrha, although there was also a tradition that he was (born from the earth); he is also said to be a son of Hellen son of Deucalion and Pyrrha. Amphictyon was king of Thermopylae and married a daughter of Cranaus of Athens. According to some accounts this daughter was named Atthis, although this conflicts with other accounts which relate that she died young as an unmarried virgin. Amphictyon eventually deposed Cranaus, proclaiming himself king of Athens.
Amphictyon had a son, Itonus, who in his turn became the father of Boeotus, Iodame and Chromia by Melanippe. He also had a daughter, never mentioned by name, who became the mother of Cercyon by Poseidon, and of Triptolemus by Rarus. Some add that Amphictyon had another son, Physcus, by Chthonopatra; others, however, state that Physcus was the grandson of Amphictyon through Aetolus.
Amphictyon ruled Athens for ten, or in some accounts, twelve years and founded the Amphictyonic League, which traditionally met at Thermopylae in historical times. During his reign, Dionysus was supposed to have visited Amphictyon in Athens and taught him how to mix water with wine in the proper proportions. Amphictyon was deposed by Erichthonius, another autochthonous king of Athens.