The Battle of Cumae was a naval battle in 474 BC between the combined navies of Syracuse and Cumae and the Etruscans.
Hiero I of Syracuse allied with Aristodemus, the tyrant of Cumae, to defend against Etruscan expansion into southern Italy. In 474 they met and defeated the Etruscan fleet at Cumae in the Bay of Naples. After their defeat, the Etruscans lost much of their political influence in Italy. They lost control of the sea and their territories were eventually taken over by the Romans, Samnites, and Gauls. The Syracusans dedicated a captured Etruscan helmet at the great panhellenic sanctuary at Olympia, a piece of armour found in the German excavations there. The Etruscans would later join the failed Athenianexpedition against Syracuse in 415 BC, which contributed even further to their decline.