Ian McKellen played Gandalf in The Lord of the Rings film trilogy.
Gandalf is a Maia sent to Middle-earth to oppose Sauron and encourage resistance against the Dark Lord. In the films, he begins as Gandalf the Grey and later returns as Gandalf the White after confronting the Balrog beneath Moria.
Gandalf helps Bilbo Baggins, recognizes the danger of the One Ring, and guides Frodo and the other members of the Fellowship. His knowledge, counsel, and ability to unite different peoples make him one of the trilogy’s central figures.
Saruman is another wizard, played by Christopher Lee, but he becomes an ally of Sauron. Radagast appears in The Hobbit films, while Elrond is an elf lord played by Hugo Weaving. Those names are therefore distinct from Gandalf.