The Battle of Spartolos () took place in 429 BC between Athens and the Chalkidian League and their allies, in the early part of the Peloponnesian War. The Athenians under Xenophon (not the famous historian and pupil of Socrates) marched into Thrace to attack Spartolos. They destroyed the crops outside and began negotiating with pro-Athenian factions in Chalcidice, but the anti-Athenian factions asked for help from Olynthus. An army from Chalcidice, Spartolos, and Olynthus met the Athenians in battle, but their hoplites were defeated and they retreated to Spartolus; their cavalry, however, was victorious against the Athenian troops. Reinforcements soon arrived from Olynthus, and they launched a second attack on the Athenians. The Athenians panicked and were routed, with all of their general