Battle of Morbihan
55 BCE.
Shown on the map at 47.500°, -2.867°.
The Battle of Morbihan, also known as the Battle of Quiberon Bay, was a naval battle fought in the summer of 56 BC between the Gallic tribe of the Veneti and a Roman fleet sent by Julius Caesar. The battle was fought off the coast of Brittany in modern-day France, likely near Quiberon Bay. The battle was a part of the Gallic Wars. The battle ended in a decisive Roman victory.
Text from the Wikipedia article Battle of Morbihan, licensed CC BY-SA 4.0.