Assassin's Creed Odyssey's main historical setting begins in 431 BCE.
That date places the game at the start of the Peloponnesian War between Athens and Sparta. The player controls Alexios or Kassandra, a mercenary connected to the Spartan royal family, while traveling through the Greek world and becoming involved in political, military, and family conflicts.
Odyssey uses a large map that includes mainland Greece and many Aegean islands. Historical figures such as Pericles, Socrates, and Hippocrates appear in the story, alongside fictional characters and the series' wider mythology.
The date can be confused with other famous ancient Greek milestones. 323 BCE is the year Alexander the Great died, while 44 BCE belongs to the late Roman Republic. Odyssey's campaign starts much earlier, when the conflict between Athens and Sparta has just begun.