How many years did the Titanomachy last?

The Titanomachy lasted ten years.

In Greek mythology, the Titanomachy was the great war between the older Titans and the younger Olympians for control of the cosmos. The standard surviving account comes from Hesiod’s Theogony, which describes the opposing sides as fighting continuously for ten full years before the conflict reached its decisive phase.

The war began after Zeus freed his swallowed siblings and recruited powerful allies. The Cyclopes forged Zeus’s thunderbolt, Poseidon’s trident, and Hades’s helmet of invisibility. The Hecatoncheires, giants with a hundred hands, also joined the Olympian side and hurled enormous volleys of stones against the Titans.

The Olympians eventually defeated Cronus and most of the Titans. The defeated gods were imprisoned in Tartarus, guarded by the Hecatoncheires, although some Titans—such as Oceanus and Prometheus in particular traditions—did not fight against Zeus. The Titanomachy is distinct from the later Gigantomachy, a separate battle between the Olympian gods and the Giants.