In which ancient region is most of Assassin's Creed Origins set?

Most of Assassin's Creed Origins is set in Ptolemaic Egypt.

The game takes place in the first century BCE, during the reign of Cleopatra VII and the political struggle involving Ptolemy XIII. Its protagonist, Bayek of Siwa, is a Medjay who becomes involved in the events that lead to the formation of the Hidden Ones, the precursor organization to the later Assassin Brotherhood.

Ptolemaic Egypt combined Egyptian traditions with Greek and Macedonian royal rule after Alexander the Great's conquests. Origins uses locations such as Alexandria, Memphis, Siwa and the Giza plateau to present that setting. Ancient Greece belongs primarily to Assassin's Creed Odyssey, while Roman Britain is the main setting of Assassin's Creed Valhalla's English sections.