Demetrias (Ancient Greek: Δημητριάς) 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

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