Battle of Zela
66 BCE.
Shown on the map at 40.300°, 35.883°.
The Battle of Zela, not to be confused with the more famous battle in 47 BC, was fought in 67 BC near Zela in the Kingdom of Pontus. The battle resulted in a stunning Pontic victory and King Mithridates' successful reclamation of his kingdom. Mithridates' victory was short-lived however, as within a few years he would be completely defeated by Pompey the Great.
Text from the Wikipedia article Battle of Zela (67 BC), licensed CC BY-SA 4.0.