Phlegra (Greek: Φλέγρα) is both a real and a mythical location in both Greek and Roman mythology.
In Greek mythology, it is the site of Zeus's overthrowing of the Giants (Gigantes) at the end of the Gigantomachy.
Plegra is a peninsula of Macedonia (more specifically in Chalkidike) in modern Greece; it is an ancient name for Pallene in historical Thrace, the latter as per the toponymy of the ancients; Pallene – and Phlegra – is most commonly called nowadays Kassandra, or Peninsula of Kassandra.
Strabo wrote that the Phlegraiean Field (Φλέγρας πεδίον, Phlegras pedion, or Φλεγραία πλάξ, Phlegraia plax) or Phlegra was in Campania near Cumae. He writes that the Giants who survived, were driven out by Heracles, finding refuge with their mother in Leuca, a town now in Italy's 'heel'. A fountain there had smelly water the locals claimed to be from the ichor of the giants.
Strabo also writes:
The peninsula Pallene, on whose isthmus is situated the city formerly called Potidaea and now Cassandreia, was called Phlegra in still earlier times. It used to be inhabited by the giants of whom the myths are told, an impious and lawless tribe, whom Heracles destroyed.
Phlegras pedion has also been used as a synonym of – or as a field in – Nephelokokkygia (cloud cuckoo land).