Sermylia (Ancient Greek: Σερμυλία), or Sermyle (Σερμύλη), was a town of Chalcidice, between Galepsus and Mecyberna. The town gave its name to the Toronaic Gulf, which was also called Sermylicus Sinus (κόλπος Σερμυλικός - kolpos Sermylikos). Pseudo Scylax writes that it was a Greek city. It was a member of the Delian League.

The site of Sermylia is near the modern Ormylia.

This article incorporates text from a publication now in the public domain: Smith, William, ed. (1854–1857). "Sermyle". Dictionary of Greek and Roman Geography. London: John Murray.

40°17′54″N 23°32′23″E/40.298222°N 23.539631°E/ 40.298222; 23.539631