The battle of Akragas (c.472-1 BC) was a clash between Heiro, tyrant of Syracuse and Thrasydaeus, tyrant of Akragas, that ended in victory for Heiro.
Theron, tyrant of Akragas, had been allied with Heiro for the last years of his rule, but in 472 BC Theron died and was succeeded by his son Thrasydaeus. The new tyrant was much less successful than his father. He had already nearly triggered a revolt when ruling Himera for his father. He was violent and murderous even during his father's life, and soon alienated the population of Akragas. Possibly in an attempt to preserve his position he employed a large number of mercenaries, but he also enlisted the citizens of Akragas and Himera, the two main cities under his command, to create an army given as 20,000 strong by Diodorus.
Thrasydaeus was planning to attack Syracuse, but Heiro landed the first blow. He raised his own army and marched west towards Akragas. The two sides met in battle. This was fought between two forces of hoplites, and must have been a lengthy hard-fought battle, for Diodorus records casualty figures of 4,000 for Akragas and 2,000 for Syracuse. The battle ended with a Syracusan victory. Thrasydaeus was forced into exile. He attempted to find safety at Nisaean Megara in Greece, but instead of finding safety he was tried and executed.
After Thrasydaeus was exiled he was replaced by an oligarchy ('the thousand'). This was replaced after three years by a democracy, which negotiated peace with Heiro.