https://www.gamespot.com/articles/e3-2018-assassins-creed-odyssey-is-set-in-ancient-/1100-6459567/

After Ubisoft's success at transporting players to the mystical lands of ancient Egypt in Assassin's Creed Origins, players have been clamoring for any hint as to the location and time period of the next game in the franchise. A few leaks and a six-second teaser left players convinced that the upcoming game, Assassin's Creed Odyssey, might take place in ancient Greece. As we learned during Ubisoft's E3 2018 press conference, it turns out those predictions were right.

Odyssey will be taking players back to ancient Greece, specifically to the middle of the Peloponnesian War around 431 BC. This places the game about 350 years after Bayek and Aya's adventure during the events of Origins, but still centuries before the rest of the franchise. The story of Odyssey will be placed against the backdrop of the conflict between Sparta and Athens, leading players to visit iconic locations like Delos, Mykonos, and Attica.