Demetrias (Ancient Greek: ) was an ancient Greek city. Demetrias may also refer to:
Battle of Demetrias, a 1270s sea battle near the Greek city Demetriapolis or Demetrias, an ancient city in Arachosia An alternative name for the city of Sicyon in the northern Peloponnesus Demetrias in Assyria, an ancient Greek colony in northern Iraq Demetrias (beetle), a genus of ground beetle Demetrias (daughter of Anicius Hermogenianus Olybrius), Roman noblewoman of the 5th century Antigonis and Demetrias, two Ancient Greek tribes