In Greek mythology, the Gigantes (Γίγαντες; singular Gigas) or, commonly, Giants, were a race of giants, children of Gaia or Gaea, who was fertilized by the blood of Ouranos when Cronus castrated him.
Gaea, incensed by the imprisonment of the Titans in Tartarus by the Olympians, incited the Gigantes to rise up in arms against them, end their reign, and restore the Titans' rule. Led on by Alcyoneus and Porphyrion, they tested the strength of the Olympians in what is known as the Gigantomachia or Gigantomachy. The Olympians called upon the aid of Heracles after a prophecy warned them that he was required to defeat the Gigantes. Heracles slew not only Alcyoneus, but dealt the death blow to the Gigantes who had been wounded by the Olympians. The Gigantes Otus and Ephialtes hoped to reach the top of Mount Olympus by stacking the mountain ranges of Thessaly, Pelion, and Ossa, on top of each other. "Power is latent violence, which must have been manifested at least in some mythological once-upon-a-time. Superiority is guaranteed only by defeated inferiors," Walter Burkert remarked of the Gigantomachy.
This battle parallels the Titanomachy, a fierce struggle between the upstart Olympians and their older predecessors, the Titans (who lost the battle). In the Gigantomachia, however, the Olympians were already in power when the Gigantes rose to challenge them. With the aid of their powerful weapons and Heracles, the Olympians defeated the Gigantes and quelled the rebellion, confirming their reign over the earth, sea, and heaven, and confining the Gigantes to the Netherworld.
Whether the Gigantomachia was interpreted in ancient times as a kind of indirect "revenge of the Titans" upon the Olympians — as the Gigantes' reign would have been in some fashion a restoration of the age of the Titans — is not attested in any of the few literary references. Later Hellenistic poets and Latin ones tended to blur Titans and Giants.
According to the Greeks of southern Italy, the Gigantes were buried by the gods beneath the earth, where their writhing caused volcanic activity and earthquakes.
In iconic representations the Gigantomachy was a favorite theme of the Greek vase-painters of the fifth century (illustration above right).
More impressive depictions of the Gigantomachy can be found in classical sculptural relief, such as the great altar of Pergamon, where the serpent-tailed giants are locked in battle with a host of gods, or in Antiquity at the Temple of Olympian Zeus at Acragas.
The Gigantes identified by individual names were Alcyoneus slain by Heracles, Porphyrion wounded by Zeus with lightning bolts and finished off by Heracles, Enceladus and Pallas killed by Athena, Polybotes crushed by Poseidon beneath the island of Nisyros, Hippolytus slain by Hermes with his sword and wearing the cap of invisibility, Ephialtes of the Aloadae shot by Apollo with arrows, Gration slain by the goddess Artemis with her arrows, Eurytos slain by Dionysos with his pine-cone tipped thyrsos, Agrios and Thoon clubbed to death by the Moirae with clubs of bronze, Mimas slain by Hephaestus with bolts of metal and Clytius by Hecate with flaming torches.