Athens and Sparta were allies during which of the following conflicts?

The Trojan War was a legendary conflict primarily involving the city of Troy and several Greek city-states, including Mycenae and Ithaca, but it occurred long before Athens and Sparta became the prominent city-states known in the classical period. Therefore, they were not allies during this mythological event.

The Syracusan War, also known as the Sicilian Expedition, was a campaign undertaken by Athens against Syracuse during the Peloponnesian War. Sparta was not allied with Athens in this conflict; rather, it was a major adversary, actively opposing Athenian expansion and involvement in Sicily.

The Messinian slave rebellion, or Helot Revolt, was a series of uprisings by the Helots against Spartan control, occurring in the 7th century BCE. During this internal conflict, Athens was not an ally but rather a separate entity with its own interests, and thus there was no cooperation between the two city-states.