Sparta is the birthplace of Alexios or Kassandra in Assassin's Creed Odyssey.
The player chooses either Alexios or Kassandra, and the selected character is the child of Myrrine and Leonidas I of Sparta. The story begins on the island of Kephallonia, but the protagonist's family identity and birth are tied to Sparta. This distinction makes Kephallonia the opening location rather than the answer to the birthplace question.
Odyssey is set in the fifth century BCE during the Peloponnesian War. The playable hero travels through a large version of the Greek world, visiting places such as Athens, Corinth, Thebes, and many islands. Sparta and Athens are especially important because the war between their alliances provides the broad historical context.
The game is a work of historical fiction. It uses real figures, locations, and political conflicts, but the protagonist, dialogue choices, branching outcomes, and supernatural elements are fictionalized. Kassandra is the canon protagonist in later series continuity, although the game lets players choose either character.