Source Verification: The Gigantomachy

Every claim below is either what a named ancient source attests, in its own line or section, or a point where the sources themselves disagree.

What the Sources Attest

What is the Gigantomachy myth?

The Gigantomachy is the Greek myth of the war between the Olympian gods and the Giants, the earth-born sons of Gaia. Apollodorus says an oracle told the gods that no Giant could die at a god's hand, only with a mortal's help, so Zeus summoned Heracles. Each god killed a named Giant, Heracles finished them with arrows, and Zeus's rule survived the challenge.

Source: Apollodorus, Library 1.6.1

Are Gigantomachy and Titanomachy the same?

No. They are two separate wars fought against two different groups. In the Titanomachy the Olympians fought the Titans, Kronos's own generation, for ten years. In the Gigantomachy they fought the Giants, whom Apollodorus says Earth brought forth after the Titans were beaten because she was vexed on their account. The Titanomachy is told most fully by Hesiod.

Source: Apollodorus, Library 1.6.1

What is the difference between the Gigantomachy and the Titanomachy?

The Titanomachy was a war among gods for rule of the cosmos, and Zeus won it by freeing the Cyclopes and Hundred-Handers from Tartarus. The Gigantomachy came afterwards and was decided differently: an oracle said the gods needed a mortal, so Zeus called Heracles. The Titans were bound in Tartarus, while the Giants were killed one by one.

Source: Apollodorus, Library 1.6.1

Who killed the giants in Greek mythology?

The Olympian gods killed them with Heracles's help. In Apollodorus, Athena and Heracles killed Alcyoneus, Zeus and Heracles killed Porphyrion, and Zeus struck down most of the rest with thunderbolts while Heracles shot them as they were dying. Apollo, Dionysus, Hecate, Hephaestus, Poseidon, Hermes, Artemis and the Fates each killed at least one named Giant.

Source: Apollodorus, Library 1.6.2

Which giant opposed which god?

Apollodorus pairs them in one passage. Athena and Heracles faced Alcyoneus and Athena also fought Enceladus and Pallas. Apollo and Heracles shot Ephialtes, Dionysus killed Eurytus, Hecate killed Clytius, Hephaestus killed Mimas, Poseidon killed Polybotes, Hermes killed Hippolytus, Artemis killed Gration, and the Fates killed Agrius and Thoas. Porphyrion fell to Zeus and Heracles.

Source: Apollodorus, Library 1.6.2

What is the difference between a giant and a Titan?

The two are different races, born differently. Hesiod says Earth bore the Titans after lying with Heaven, including Kronos and Rhea. The Giants came from the blood that fell on Earth when Kronos wounded his father, and Hesiod pictures them in gleaming armour with long spears. The Titans ruled before Zeus. The Giants only attacked his rule.

Source: Hesiod, Theogony 183-187

Where Accounts Differ

birth-of-the-giants
where-the-war-was-fought
who-killed-porphyrion-and-mimas
giants-serpent-feet-or-not
ovid-version-without-heracles

The Giants' birth is told two ways. Hesiod, Theogony 183-187, has them spring from the blood of Ouranos's wound. Apollodorus, Library 1.6.1, says Earth bore them by Sky. This page gives both and does not choose one.
Where the war was fought is disputed. Apollodorus, Library 1.6.1, says the Giants were born in Phlegrae according to some and in Pallene according to others. Pindar, Nemean 1.67-72, has the battle on the plain of Phlegra. Pausanias, Description of Greece 8.29.1, reports that the Arcadians place it near their own Bathos, not at Pellene in Thrace.
Who killed Porphyrion differs. Apollodorus, Library 1.6.2, has Zeus strike him with a thunderbolt and Heracles finish him with an arrow. Pindar, Pythian 8.12-18, names the king of the Giants and gives his defeat to Apollo's bow, setting it beside Zeus's thunderbolt against Typhon. In the note to 1.6.2, Frazer records that other sources also give Mimas's death to Zeus (Euripides's Ion) or to Ares (Apollonius Rhodius and Claudian) rather than to Hephaestus.
The Giants' form differs. Apollodorus, Library 1.6.1, gives them dragons' scales for feet. Pausanias, Description of Greece 8.29.3, calls that an absurd tale and argues the Giants were mortal men of great size. Frazer notes that later monuments often show them serpent-footed, and Hesiod's armoured Giants have no serpent feet at all.
Ovid, Metamorphoses 1.89-162, tells a different war. The Giants pile mountains against heaven, Jove shatters them with thunderbolts, and Earth makes men from their blood. There is no oracle, no Heracles and no roll of duels. This page follows Apollodorus for the details and marks where Ovid departs.

Sources

Primary sources

Apollodorus, Library 1.6.1
Apollodorus, Library 1.6.2
Apollodorus, Library 1.6.3
Hesiod, Theogony 132-138
Hesiod, Theogony 183-187
Pindar, Nemean Odes 1.67-72
Pindar, Pythian Ode 8.12-18
Ovid, Metamorphoses 1.89-162
Pausanias, Description of Greece 8.29.1-3