Murena was a praetor probably in 88 BC. was a lieutenant of Lucius Cornelius Sulla during the First Mithridatic War (89–85 BC) with Mithridates VI of Pontus. He participated in the Battle of Chaeronea of 86 BC. Sulla encamped near Chaeronea, close to the camp of Archelaus, the commander of the enemy. He left Murena behind with one legion and two cohorts to face the enemy, should they prepare for battle, and went to Chaeronea, where the Romans had a garrison. Some of the townsfolk offered to go and cut off the enemy at nearby Thurium. Sulla agreed, returned to his camp and prepared for battle, putting Murena in charge of the left wing. The Chaeroneans were routed and Murena received some of the fugitives. During the battle Murena was attacked and Sulla sent four cohorts to help him. Later in the battle he set out to help him himself. However, Murena had already gained the upper hand and Sulla joined him in the pursuit of the fugitives.