The Delian League, founded in circa 477 BCE, is an association of Greek city-states, members numbering between 150 to 173, under the leadership of Athens, whose purpose is to continue fighting the Persian Empire after the Greek victory in the Battle of Plataea at the end of the Second Persian invasion of Greece.

The League's modern name derives from its official meeting place, the island of Delos, where congresses are held in the temple and where the treasury stands until, in a symbolic gesture, Pericles moves it to Athens in 454 BCE.

Shortly after its inception, Athens begins to use the League's navy for its own purposes.

This behavior frequently leads to conflict between Athens and the less powerful members of the League.

By 431 BCE, Athens' heavy-handed control of the Delian League prompts the outbreak of the Peloponnesian War; the League is dissolved upon the war's conclusion in 404 BCE.