Much of modern historical literature describes the ancient Adriatic Sea as a region beset by piracy, primarily Illyrian piracy. This view is supported by a number of ancient writers, beginning with Polybius. However, the pre-Hellenistic (Classical) evidence, humble though it is, does not seem to confirm it. The paper examines and confronts two groups of sources, one earlier, from the 4th century BC, and the other from the 2nd century BC onward. The main thesis is that Polybius and other later authors tend to exaggerate the volume and importance of early Illyrian piracy, being influenced by the knowledge of the achievements of the 3rd century BC rulers of the Ardiaei and by the general ideological perspective on the enemies of Rome.

Keywords: Adriatic Sea, Piracy, Illyrians, Polybius, Diodorus.