In Greek mythology, Gigantomachy (from Greek: gigantomakhia, from gigas Giant and makhē battle) was the symbolic struggle between the cosmic order of the Olympians led by Zeus and the nether forces of Chaos led by the giant Alcyoneus. Heracles fought on the side of Olympians, who defeated the Giants in accordance with Hera's prophecy that the gods' victory would not be accomplished without the participation of the son of a mortal mother. Pallene was regarded as the Giants' home ground during the Gigantomachy; their leader Alcyoneus could not be defeated in his homeland, so Heracles picked him up and carried him over the border out of Pallene, and slaughtered him there. The attempt of the Giants Otus and Ephialtes to storm Olympus by piling Mount Ossa upon Mount Pelion is linked with the Gigantomachy in some sources, and treated as a separate, adolescent attack upon the power of Zeus in others.
After the Titanomachy, the goddess Gaia, seeking revenge, brought forth the Giants, including Enceladus and Porphyrion, telling them to "take arms against the great gods". Hesiod describes them as "glittering in their armour, with long spears in their hands." They could only be defeated by a god and a hero working together.
The Gigantomachy became a popular theme from the early 7th century BC (including the so-called Gigantomachy pediment on the Acropolis). A temple at Phanagoreia commemorated Aphrodite's victory over some Giants. She drove them into a cave, where Heracles slaughtered them. After the Greco-Persian Wars the representation of Gigantomachy symbolized the hostility between the Greeks and the Persians, with the Greeks figuring as the Olympians, and the Persians as Giants. Additionally, in the dialogue Sophist, Plato's interlocutor the Eleatic Stranger references this battle as a battle between atomists like Epicurus and philosophers who believed in eternal forms like Plato himself.
Following the fashions, originally developed in Hellenistic Alexandria, for rationalized glosses on the archaic myths and for allegorical interpretations, the fifth-century court poet of emperor Honorius, Claudian, composed a Gigantomachia, that viewed Gigantomachy as a metaphor for catastrophic geomorphic change: "The puissant company of the giants confounds all differences between things; islands abandon the deep; mountains lie hidden in the sea. Many a river is left dry or has altered its ancient course....robbed of her mountains Earth sank into level plains, parted among her own sons." 
In the Inferno this is referenced when Dante sees chained Giants before he reaches the Ninth and last Circle of Hell, which is for Traitors. This is probably meant to be compared to Lucifer's rebellion, as later on in the Circle Dante witnesses Satan.
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- Karl Kerenyi, The Gods of the Greeks, 1951:28–30; Gigantomachy: Sculpture & Vase Representations
- Ps-Apollodorus, Bibliotheke, 1.6.1.
- During the battle Ephialtes is wounded in his left eye by Apollo, and in his right by Heracles (Karl Kerenyi, The Gods of the Greeks, 1951, p.30).
- Apollo "laid both giants low before their beards had sprouted" according to Homer Odyssey xi. 305 (line 362 in Robert Fagles' translation).
- The Giants are an "army of avengers" in Claudian's truncated Gigantomachia.
- Ovidius, Fasti, 5.38.
- Hesiod, Theogony, 186.
- Philip Mayerson. Classical mythology in literature, art, and music, Focus publishing, R. Pullins Company, 2001, p. 68
- See, for examples, Euhemerus and Diodorus' historicized treatment of myth.
- theoi Project: Gigantomachia text