In Greek mythology, the Titanomachy ( Greek: Titanomakhia, "Titan battle") was a ten-year series of battles fought in Thessaly, consisting of most of the Titans (an older generation of gods, based on Mount Othrys) fighting against the Olympians (the younger generations, who would come to reign on Mount Olympus) and their allies. This event is also known as the War of the Titans, Battle of the Titans, Battle of the Gods, or just the Titan War. The war was fought to decide which generation of gods would have dominion over the universe; it ended in victory for the Olympian gods.
Greeks of the Classical Age knew of several poems about the war between the gods and many of the Titans. The dominant one, and the only one that has survived, is the Theogony attributed to Hesiod. The Titans also played a prominent role in the poems attributed to Orpheus. Although only scraps of the Orphic narratives survive, they show interesting differences from the Hesiodic tradition.
Uranus drew the enmity of Gaia when he imprisoned her children the Hecatonchires and Cyclopes in Tartarus. Gaia created a great sickle and gathered together Cronus and his brothers to convince them to castrate Uranus. Only Cronus was willing to do the deed, so Gaia gave him the sickle and placed him in ambush.
When Uranus met with Gaia, Cronus attacked Uranus, and, with the sickle, cut off his genitals, casting them into the sea. In doing so, he became the King of the Titans. But Uranus made a prophecy that Cronus's own children would rebel against his rule, just as Cronus had rebelled against his own father. Uranus' blood that had spilled upon the earth, gave rise to the Gigantes, Erinyes, and Meliae. From his semen or blood of his cut genitalia, Aphrodite arose from the sea:
...so soon as he had cut off the members with flint and cast them from the land into the surging sea, they were swept away over the main a long time: and a white foam spread around them from the immortal flesh, and in it there grew a maiden..."
Cronus took his father's throne after dispatching Uranus. He then secured his power by re-imprisoning his siblings the Hecatonchires and Cyclopes in Tartarus.
Cronus, paranoid and fearing the end of his rule, now turned into the terrible king his father Uranus had been, swallowing each of his children whole as they were born from his sister-wife Rhea. Rhea, however, managed to hide her youngest child Zeus, by tricking Cronus into swallowing a rock wrapped in a blanket instead.
Rhea brought Zeus to a cave in Crete, where he was raised by Amalthea. Upon reaching adulthood, he masqueraded as Cronus' cupbearer. Once Zeus had been established as a servant of Cronus, Metis gave him a mixture of mustard and wine which would cause Cronus to vomit out his swallowed children, now grown. After freeing his siblings, Zeus led them in rebellion against the Titans.
Zeus then waged a war against his father with his disgorged brothers and sisters as allies: Hestia, Demeter, Hera, Hades, and Poseidon. Zeus released the Hecatonchires and the Cyclopes from the earth (where they had been imprisoned by Cronus) and they allied with him as well. The Hecatonchires hurled stones, and the Cyclopes forged for Zeus his iconic thunder and lightning. Fighting on the other side allied with Cronus were the other Titans with the important exception of Themis and her son Prometheus who allied with Zeus (NB. for Hesiod, Clymene is the mother of Prometheus). Atlas was an important leader on the side of Cronus. The war lasted ten years, but eventually Zeus and the other Olympians won, the Titans were imprisoned in Tartarus, and the Hecatonchires were made their guards. Atlas was given the special punishment of holding up the sky. In some accounts, when Zeus became secure in his power he relented and gave the Titans their freedom.
Hyginus relates the Titanomachy differently: "After Hera saw that Epaphus, born of a concubine, ruled such a great kingdom (Egypt), she saw to it that he should be killed while hunting, and encouraged the Titans to drive Zeus from the kingdom and restore it to Cronus (Saturn). When they tried to mount heaven, Zeus with the help of Athena, Apollo, and Artemis, cast them headlong into Tartarus. On Atlas, who had been their leader, he put the vault of the sky; even now he is said to hold up the sky on his shoulders."
Following their final victory, the three brothers divided the world amongst themselves: Zeus was given domain over the sky and the air, and was recognized as overlord. Poseidon was given the sea and all the waters, whereas Hades was given the Underworld, the realm of the dead. Each of the other gods was allotted powers according to the nature and proclivities of each. The earth was left common to all to do as they pleased, even to run counter to one another, unless the brothers (Zeus, Poseidon and Hades) were called to intervene.
A somewhat different account of the Titanomachy appeared in a poem that is now lost. The poem was traditionally ascribed to Eumelus of Corinth, a semi-legendary bard of the Bacchiad ruling family in archaic Corinth, who was treasured as the traditional composer of the Prosodion, the processional anthem of Messenian independence that was performed on Delos.
Even in Antiquity many authors cited Titanomachia without an author's name. The name of Eumelos was attached to the poem as the only name available. From the very patchy evidence, it seems that "Eumelos"' account of the Titanomachy differed from the surviving account of Hesiod's Theogony at salient points. It was written in the late seventh-century BC at the earliest.
The Titanomachy was divided into two books. The battle of Olympians and Titans was preceded by some sort of theogony, or genealogy of the Primeval Gods, in which, the Late Roman writer Lydus remarked, the author of Titanomachy placed the birth of Zeus, not in Crete, but in Lydia, which should signify on Mount Sipylus.