Which Titan castrated his father Ouranos?

Cronus was the Titan who castrated his father, Ouranos.

Hesiod’s Theogony says that Ouranos imprisoned or concealed his children within Gaia, causing her anguish. Gaia fashioned an adamantine sickle and asked her children to oppose him. Cronus, the youngest of the twelve Titans, accepted the task and ambushed Ouranos when he came to lie with Gaia.

Cronus castrated his father and cast the severed genitals into the sea. This act ended Ouranos’s rule and enabled the Titans to take control of the cosmos, with Cronus becoming their leader. In the myth’s violent succession pattern, the overthrow also foreshadows Cronus’s own eventual defeat by his son Zeus.

Cronus should not be confused with Chronos, a personification of time found in some later traditions. Nor is he the same as Zeus, who eventually leads the Olympians against the Titans. Cronus married his sister Rhea and fathered Hestia, Demeter, Hera, Hades, Poseidon, and Zeus. Because he feared a prophecy that one of his children would overthrow him, he swallowed them—until Rhea saved Zeus.