Hiero I is the son of Deinomenes, the brother of Gelo and tyrant of Syracuse in Sicily from 478 to 467 BCE.

In succeeding Gelon, he conspired against a third brother Polyzelos.

During his reign, he greatly increased the power of Syracuse.

He removed the inhabitants of Naxos and Catana to Leontini, peopled Catana (which he renamed Aetna) with Dorians, concluded an alliance with Acragas (Agrigentum) and espoused the cause of the Locrians against Anaxilas, tyrant of Rhegium.