Ptolemais Hermiou was established on the west bank of the Nile at the site of the Egyptian village of Psoï in the Thinis nome by the Ptolemaic ruler Ptolemy I Soter sometime after 312 BCE.

[2] Whether it was intended from the outset to replace Thebes as a political centre is disputed.

[3] The name Hermiou could refer to a person called Hermias that could have coordinated the foundation for Ptolemy.

[4] According to Strabo, it was the largest city in the Thebaid, equal to Memphis in size.

[6] The city housed temples to Greek and Egyptian gods (Zeus, Dionysus, Isis) as well as a cult for the worship of the Ptolemaic Dynasty.