Glaucias was a ruler of the Taulantian kingdom, situated in modern day Albania, which dominated southern Illyrian affairs in the second half of the 4th century BC. Glaucias is first mentioned as bringing a considerable force to the assistance of Bardylis' son Cleitus, an Illyrian prince who revolted against Alexander the Great, in the battle of Pelium 335 BC. They were, however, both defeated, and Cleitus was forced to take refuge within the Taulantian territories, whither Alexander did not pursue him, his attention being called elsewhere by the news of the revolt of Thebes.