In Ursula K. Le Guin’s Earthsea, the protagonist’s true name is Ged.
Ged is introduced in A Wizard of Earthsea as a gifted but proud boy from the island of Gont. His childhood name is Duny, while Sparrowhawk is the use-name by which he becomes widely known. At his naming ceremony, the wizard Ogion gives him the true name Ged, an identity with deep magical significance in Earthsea.
Earthsea’s naming system is central to its magic. A person’s true name expresses their essential self and is normally kept secret, because someone who knows it may gain power over them. Ged’s story follows his movement from reckless ambition toward humility, responsibility, and wisdom.
The answer should not be replaced by Sparrowhawk: that is Ged’s use-name, not his true name. Vetch is a fellow wizard and friend, while Ogion is Ged’s mentor. Some adaptations alter or confuse the naming conventions, but in Le Guin’s original fiction, Ged is the canonical true name.