Demetrius of Scepsis was a Greek scholar and antiquarian active in the early Hellenistic period, around 200 BCE. He came from the town of Scepsis in northwestern Asia Minor and was a student of the famous Alexandrian scholar Aristarchus of Samothrace. This education placed him within the influential traditions of the Library of Alexandria and the Peripatetic school, which emphasized detailed, systematic research.

His major work was the Trojan Order, a massive 30-book treatise. It was a detailed commentary on the catalog of Trojan allies found in Homer's Iliad. The work combined Homeric criticism with geography and antiquarian research, focusing intensely on the history and landscape of the Trojan region. The treatise itself is now lost, surviving only through fragments quoted by later authors.

Demetrius is a significant figure in the history of classical scholarship. His meticulous work on Homeric geography became a major source for later writers, most notably the geographer Strabo, who frequently cited and debated his conclusions. Through these citations, Demetrius's research helped shape the ancient understanding of the Homeric world. According to modern scholars, his methodology exemplifies the application of Alexandrian erudition to literary and historical problems, using detailed argumentation about place names and historical changes in the landscape.