The battle of Argolas (Spring 354 BC) was a Phocian victory over a Thessalian army early in the Third Sacred War, fought at an otherwise unknown hill somewhere in Locris. Our account of this battle comes from Diodorus (16.30).
In 355 the Phocians seized the Oracle of Delphi, and then defeated a Locrian army at Phaedriades, near to the Oracle. This setback for the Amphictyonic Council may have helped convince the Thessalians and Thebans to join the conflict to support the League, while Sparta and Athens sided with the Phocians.
In 355 the Phocian leader Philomelus had made a point of not looting the treasures of the oracle, but in 354 he decided that he needed the money to raise a more powerful army. He used the extra funds to hire more mercenaries. This gave him an army of over 10,000 men, which he led into Locris.
The first clash of the new campaign was a cavalry battle between the Phocians on one side and the Locrians and Boeotians on the other. This ended in a Phocian victory, but the location isn't recorded.
The second battle of the campaign came near a hill called Argolas, which isn't mentioned in other ancient sources. This time the Phocians faced 6,000 Thessalians and allies, suggesting that this battle was somewhere to the north.
Diodorus provides us with very little detail of this battle, other than the unknown name of its location, and the fact that the Thessalians were defeated.
Philomelus's run of luck finally came to an end later in the year. The Boeotians finally appeared on the scene, and defeated the Phocians at Neon (north of Mount Parnassus). In order to avoid capture, Philomelus threw himself off a cliff.