| Conflict: | Battle of Thermopylae (254) |
| Partof: | the Crisis of the Third Century Gothic War (248-253) and Roman–Germanic Wars |
| Battle Name: | Battle of Thermopylae |
| Date: | 254 |
| Place: | Thermopylae, Achaea, Roman Empire (present-day Thermopylae, Greece) |
| Result: | Roman victory |
| Combatant1: | Roman Empire |
| Combatant2: | Goths |
| Commander1: | Marianus Philostratus Dexippus |
| Commander2: | Unknown |
| Strength1: | Militia |
| Strength2: | Unknown |
| Casualties1: | Unknown |
| Casualties2: | Unknown |
The Battle of Thermopylae in 254 was a successful defense of the pass of Thermopylae by local Greek militia under Marianus, the Roman proconsul of Achaea, during an invasion of the Balkans by the Goths.
In 254 the Goths invaded and plundered Thrace and Macedonia. In 1979, Herwig Wolfram regarded 254 as the date, while Mallan and Davenport in 2015 suggested 262. Goltz and Hartmann estimated 254 as the date. David Potter in 2016 rejected Mallan and Davenport's estimate and dated it to either 253 or 259. The Goths attempted to storm Thessalonica with close order formations and assault columns. The Thessalonians mobilized to defend their city and beat off the attacks. The Goths abandoned the siege and moved off to invade Greece south of Thermopylae, seeking to loot the gold and silver wealth of Greek temples.
The Greeks learned of the Goths' approach and the Roman proconsul Marianus, the Athenian Philostratus, and the Boeotian Dexippus mobilized a militia to block the pass of Thermopylae. The militia were armed with bronze or iron-tipped wooden pikes, small spears, axes, and assorted weapons. They set to work fortifying the pass. Marianus gave a pre-battle speech to them, emphasizing the defense of the pass by previous generations of Greeks and Romans.
The Graeco-Roman forces successfully blocked the Goths' way at Thermopylae and the Goths returned home, albeit with considerable loot.
A fragment of text attributed to the contemporary historian Dexippus, discovered in Vienna in 2010, provides detail on the weapons, leadership, and geography of the engagement. The fragment cuts off before the battle's outcome. Dexippus was used as a source by the Byzantine chronicler George Syncellus, who mentioned the blocking of the pass and the Goths' return home with plunder.