Gyges was one of the three Hecatoncheires ("Hundred-Handers"), monstrous giants of Greek mythology also called Centimanes. Like his brothers Cottus and Briareus, he possessed enormous size and strength, with fifty heads and one hundred arms sprouting from his shoulders.

The Hundred-Handers play a pivotal part in the mythological succession of cosmic power: rejected and imprisoned by their father, they were eventually released by Zeus and became the decisive allies of the Olympians in their war against the Titans. Later Roman poets such as Horace invoke the "hundred-handed" (centimanus) Gyges as a byword for overwhelming power and dread.

Gyges was a son of Uranus (Sky) and Gaia (Earth). According to Hesiod's Theogony, he and his brothers Cottus and Briareus were among the last children born to this primordial couple, following the twelve Titans and the three Cyclopes.

Hesiod describes their birth: from Earth and Sky came three great and mighty sons — Cottus, Briareus, and Gyges — from whose shoulders sprang a hundred arms, unapproachable, and upon whose massive limbs grew fifty heads.

Uranus despised his monstrous offspring and bound them underground, indignant at their defiant strength, their form, and their size. They remained imprisoned through the reign of the Titans under Cronus.

When Zeus and the Olympians fought the Titans, Gaia prophesied that the aid of the Hundred-Handers would bring victory. Zeus freed them from their bonds, and they took up positions against the Titans holding enormous boulders. In the Titanomachy they hurled three hundred rocks from their massive hands one after another, overshadowing the Titans with their missiles and helping to ensure the Olympians' triumph.

After the Titans were defeated, the Hundred-Handers were stationed at the bronze gates of the Titans' prison in Tartarus, where they took up the role of the Titans' jailers and guards.