Glaucus the Historian was a Hellenistic author of the 2nd century BCE from Rhegium in southern Italy. His existence is confirmed solely by a citation from the grammarian Didymus Chalcenterus, who worked in the late 1st century BCE, establishing Glaucus as a predecessor. No other biographical details survive.

His only known work is the lost treatise On Ancient Poets and Musicians. Surviving fragments indicate it was a scholarly work of literary and musical history. Glaucus’s significance rests entirely on his utility as a source for later scholars. His work was used by Didymus and likely influenced subsequent Alexandrian grammarians.

The fragments provide minor evidence for ancient scholarship on poetry and music, and he is occasionally cited in modern studies of Alexandrian sources and ancient music historiography.