The Battle of Chalcedon was a naval battle in 74 BC during the Third Mithridatic War. It ended in Pontic victory.
After resuming the war, consul Marcus Aurelius Cotta took Roman fleet into the Bosphorus. Outside the harbour of Chalcedon he was beaten by the Pontic fleet; Roman ships sought refuge inside the harbour, but to no avail: the Pontic fleet made their way into the port, where they destroyed or captured the Roman fleet. After the victory, Mithridates moved against the Roman controlled town of Cyzicus, which he besieged. This led to the battle of Cyzicus.