Gandalf is the wizard who guides Frodo in J.R.R. Tolkien's The Lord of the Rings.
Gandalf the Grey helps identify the danger posed by Bilbo's ring and urges Frodo to leave the Shire. He later joins the Fellowship of the Ring and takes a central role in the struggle against Sauron. His knowledge, courage, and alliances make him one of the story's most important guides.
Gandalf is one of the Istari, supernatural beings sent to Middle-earth to oppose Sauron. After confronting the Balrog in Moria, he returns as Gandalf the White. Saruman is also an Istar but becomes an enemy, while Radagast has a more limited role in the narrative.