Bayek is a Medjay in Assassin's Creed Origins.
A Medjay was historically associated with Nubian desert peoples, and by the Ptolemaic period the term had become a title for a local protector or law-enforcement figure. Bayek serves as the Medjay of Siwa, a role that gives him authority and responsibility within the oasis community.
The game's story begins in 49 BCE, when Bayek and his wife Aya become entangled in a conspiracy involving powerful figures in Egypt. Their investigation eventually contributes to the creation of the Hidden Ones, the organization that later develops into the Assassin Brotherhood.
Medjay is not the same as pharaoh, vizier, or nomarch. Those terms describe other offices or ranks in ancient Egyptian and Hellenistic political systems. Bayek's title identifies him as a protector rather than Egypt's monarch.