What is a Cyclops in Greek mythology?

What the name means

Kyklops means “round eye” in Greek; the plural is Cyclopes. The poet who spells out both the name and the single eye is Hesiod, in the Theogony, his poem about the birth of the gods.

in all else they were like the gods, but one eye only was set in the midst of their fore-heads. And they were surnamed Cyclopes (Orb-eyed) because one orbed eye was set in their foreheads.

Their names are thunder words. Brontes is the Thunderer, Steropes the Lightener and Arges the Vivid One, as Evelyn-White glosses them.

Hesiod’s smiths

In Hesiod the Cyclopes are children of Earth and Sky, brothers of the Titans and of the Hundred-Handers. Sky buries his children inside the earth, and the Cyclopes stay prisoners even after Kronos takes power. Zeus sets them free, and they repay him with the weapon that wins his war against the Titans: they “gave Zeus the thunder and made the thunderbolt” (Theogony 139–146, 501–506). That war is told on the difference between Titans and Olympians.

Later writers kept them at the forge. Apollodorus adds that they gave Hades a helmet and Poseidon his trident (Library 1.2.1). Virgil sets them hammering in Vulcan’s workshop, in caverns under a smoking island off Sicily (Aeneid 8.416–453). And the story of Asclepius, struck down by Zeus’s thunderbolt, ends with his father Apollo killing the Cyclopes who made it (Apollodorus 3.10.4).

Homer’s shepherds

Homer’s Cyclopes are a different people. They live on a fertile island, each in a cave high on the mountains, with no laws, no assemblies and no ships. They neither plow nor plant, and each rules his own wife and children without a thought for his neighbors (Odyssey 9.106–115). They do not fear the gods, as Polyphemus boasts to Odysseus. Curiously, Homer never stops to describe the single eye. He just speaks of the giant’s eye and lets his listeners picture the rest.

Polyphemus is the biggest of them, a shepherd who keeps apart even from the others. His father is Poseidon and his mother the sea nymph Thoosa, daughter of Phorcys (1.68–73). In one sentence: Odysseus gets him drunk, tells him his name is Nobody, blinds him and escapes under his rams, the whole trick told on how Odysseus tricked the Cyclops. Blinding the son is what turns the father into Odysseus’s enemy.

Later Cyclopes

Greek and Roman writers kept reinventing them. Euripides’ Cyclops, the only satyr play to survive complete, turns the cave story into a comedy with a chorus of satyrs. The poet Theocritus, and later Ovid in book 13 of the Metamorphoses, made Polyphemus a lovesick giant courting the sea nymph Galatea.

Later Greeks also credited the Cyclopes with the colossal walls of Mycenae and Tiryns, built of blocks they thought no human could lift (Pausanias 2.16.5, 2.25.8). Archaeologists still call that kind of masonry Cyclopean. So the same name covers three ideas: Hesiod’s Cyclopes arm the king of the gods, Homer’s defy him, and the builders’ Cyclopes explain stones too big to believe.