Agesilaus II was king of Sparta from c. 400 to c. 360 BC. Generally considered the most important king in the history of Sparta, Agesilaus was the main actor during the period of Spartan hegemony that followed the Peloponnesian War. Although brave in combat, Agesilaus lacked the diplomatic skills to preserve Sparta's position, especially against the rising power of Thebes, which reduced Sparta to a secondary power after its victory at Leuctra in 371 BC.

Spartan hegemony refers to the period of dominance by Sparta in Greek affairs from 404 to 371 BC. Even before this period the polis of Sparta was the greatest military land power of classical Greek antiquity and governed, dominated or influenced the entire Peloponnese. The defeat of the Athenians and the Delian League in the Peloponnesian War in 431–404 BC resulted in a short-lived Spartan dominance of the southern Greek world from 404 to 371 BC. Due to their mistrust of others, Spartans discouraged the creation of records about their internal affairs. The only histories of Sparta are from the writings of Xenophon, Thucydides, Herodotus and Plutarch, none of whom were Spartans. Plutarch was writing several centuries after the period of Spartan hegemony had ceased. This creates difficulties in understanding the Spartan political system, which was distinctly different from any other Greek polis.