Dascylium (Greek: Δασκύλιον, Δασκυλεῖον) was a town in Anatolia some 30 kilometres inland from the coast of the Propontis, at modern Ergili, Turkey. Its site was rediscovered in 1952 and has since been excavated.
Excavations have shown that the site was inhabited in the Bronze Age. Phrygians settled there before 750 BC. It came under the control of Lydia. It was then said to be named after Dascylus, the father of Gyges.
After the Conquests of Cyrus the Great in 547 BC, Dascylium was chosen as the seat of the Persian satrapy of Hellespontine Phrygia, comprising lands of the Troad, Mysia and Bithynia.
Pharnabazus was satrap of Darius III there, until Alexander the Great appointed Calas, who was replaced by Arrhidaeus in the Treaty of Triparadisus. According to Strabo, Hellespontine Phrygia and Phrygia Epictetus comprised Lesser Phrygia (Mysia). Others geographers arranged it differently.
When Alexander of Macedon invaded Asia in 334 BC, the first of the major battles by which he overthrew the Achaemenid Empire was fought at the Granicus river on his way to Dascylium from Abydos on the coast.