Amyrtaeus of Sais (Greek: Ἀμυρταῖος Amyrtaios, a Hellenization of the original Egyptian name Amenirdisu) is the only pharaoh of the Twenty-eighth Dynasty of Egypt[1] and is thought to be related to the royal family of the Twenty-sixth Dynasty (664–525 BC).

[1][8] Before assuming the throne of Egypt, Amyrtaeus had revolted against the Persian King Darius II (423–404 BC) as early as 411 BC, leading a guerrilla action in the western Nile Delta around his home city of Sais.

[2] According to Isocrates, Artaxerxes II assembled an army in Phoenicia under the command of Abrocomas to retake Egypt shortly after coming to the Persian throne, but political problems with his brother Cyrus the Younger prevented this from taking place, allowing the Egyptians sufficient time to throw off Achaemenid rule.

In 1st century BC, the Greek historian Diodorus Siculus wrote in his Bibliotheca historica (XIV, 35.3–5) that a King named Psamtik — which seems to be identified with Amyrtaeus,[1] perhaps being "Psamtik" his lost regnal name[7] — murdered the Greek admiral Tamos who had taken refuge in Egypt after the defeat of the rebel Cyrus.

[7] Amyrtaeus was defeated in open battle by his successor, Nepherites I of Mendes[12] and executed at Memphis, an event which the Aramaic papyrus Brooklyn 13 implies occurred in October 399 BC.