Dorylaeum or Dorylaion (Greek: Δορύλαιον) was an ancient city in Anatolia. It is now in ruins near the city of Eskişehir, Turkey.

The city existed under the Phrygians but may have been much older. It was a Roman trading post. It also was probably a key city of the route the Apostle Paul took on his Second Missonary Voyage in 50 AD.

Later Dorylaeum became a bishopric under the Byzantine Empire. After the Battle of Manzikert in 1071 it was taken by the Seljuk Turks.

Dorylaeum was the site of two battles during the crusades. In 1097, during the First Crusade, the crusaders defeated the Seljuks there, in their first major victory. During the Second Crusade it was the site of a major defeat, which effectively ended the German contribution to the crusade.

Byzantine emperor Manuel I Comnenus fortified Dorylaeum in 1175, but according to some authorities the Turks recaptured it in 1176 after the Battle of Myriokephalon. However, the contemporary Byzantine historian Niketas Choniates relates that Manuel did not destroy the fortifications of Dorylaeum, as he had agreed to do as part of the treaty he negotiated with the Seljuk Turkish sultan Kilij Arslan II immediately after Myriokephalon. The sultan's response to this development was not a direct attack on Dorylaeum but the dispatch of a large army to ravage the rich Meander valley to the south.