The battle of Coroneia (c.352) was the second in a series of defeats suffered by the Phocian leader Phayllus during a failed invasion of Boeotia (Third Sacred War).
In 353 BC the Phocian leader Onomarchus was defeated and killed by Philip II of Macedon at the battle of the Crocus Field in Thessaly. He was succeeded by his brother Phayllus, who managed to gather a fresh army. This was a mix of troops from his allies (1,000 from Sparta, 2,000 from Achaea and 5,000 infantry and 400 cavalry from Athens), 2,000 men led by the defeated Tyrants of Pherae, and mercenaries hired using the treasure from Delphi.
Phayllus led this new army on unsuccessful invasion of Boeotia. Diodorus lists three defeats in a row. The first came at Orchomenus, on the north-western shores of Lake Copais. The second was on the Cephisus River, which flows into the lake from the west, and then runs east and north from the lake into the sea. Next came the defeat at Coroneia, to the south of the lake. Diodorus doesn't tell us which stretch of the river the middle battle was fought on. Given the general Phocian tendancy towards aggressive behaviour, the most likely course of events is perhaps that they moved east after the defeat at Orchomenus in an attempt to win a victory further into Boeotian territory, suffered the defeat on the Cephisus River east of the lake, and then were caught a third time at Coroneia while attempting to return home along the southern shore of the lake.
As with the previous two battles, we get very few details of the battle at Coroneia. Diodorus reports that the Phocians lost 50 dead and 130 prisoners (16.37.6), suggesting that this was either a more even affair or a smaller battle than the fight on the Cephisus River, where the Phocians suffered 500 dead and lost 400 prisoners.
These defeats didn't discourage Phayllus. Probably in the same year he invaded Epicnemidian Locris (on the coast between Thermopylae and the mouth of the Cephisus River). During this campaign he captured all of the local cities apart from Naryx. Here he was let into the city by a traitor, but then expelled with the loss of 200 men.