Nea Anchialos () is a town and a former municipality in Magnesia, Thessaly, Greece. Since the 2011 local government reform it is part of the municipality Volos, of which it is a municipal unit. It is situated southwest of Volos and north of Almyros, on the Pagasetic Gulf. The area of the municipal unit is and its population 5,881 people (2021).
thumb|280px|View of Anchialos from the Pagasetic Gulf
History
Antiquity
The modern town is built on the ruins of the ancient city of Pyrasos (Πύρασος), and is associated with the nearby city of Thessalian or Phthiotic Thebes, near the modern village of Mikrothivai.
Homer mentions Pyrasos in his list of ships (Iliad B.695) together with Phylace and Itona, which belonged to the kingdom of Protesilaus. According to Strabo (IX.435), who discusses its topography, "well-harboured Pyrasos" (εὑλίμενος Πύρασος) was 20 stadia from Phthiotic Thebes.
Pyrasos is scarcely known from historical sources, except that it was an active harbour and featured a famous temple of Demeter and Kore, after which the harbour was later known as Demetrion.