Battle of Mons Seleucus
353 CE.
Shown on the map at 44.460°, 5.736°.
The Battle of Mons Seleucus was fought in 353 between the armies of the Roman emperor Constantius II and the usurper Magnentius. Constantius' forces were victorious. Support for Magnentius had been eroding since his defeat at the Battle of Mursa Major two years prior; after Mons Seleucus his cause collapsed and he killed himself.
Text from the Wikipedia article Battle of Mons Seleucus, licensed CC BY-SA 4.0.