Gandalf is a character in J.R.R. Tolkiens novels The Hobbit and The Lord of the Rings. He is a wizard, one of the Istari order, and the leader of the Fellowship of the Ring. Gandalf was originally known as Olórin and was one of the Maiar who served Manwë, Varda, Irmo, and Nienna. He was sent to Middle-earth by the Valar in the Third Age to aid and inspire the Free Peoples of Arda who resisted evil. Gandalf is known for his immense magical power, wisdom, and true heart. He is brave, quick to anger, and a formidable enemy, but he is also good-natured, spirited, and quick to laugh. Gandalf is integral to the plot of the Lord of the Rings trilogy, and he makes appearances in The Hobbit, The Silmarillion, Unfinished Tales, and The History of Middle-earth.

Gandalf is originally robed in grey, and second to Saruman in the Order of Wizards. After his fall in Moria, Gandalf returns to Middle-earth as head of the Order, robed in white. Gandalfs staff is as much a part of his character as his long beard and pointed hat. His staff has dual purposes, as a weapon and as a tool for casting spells.

Gandalf is a Maia, which means he is basically an angel/demigod. He was created by Eru Ilúvatar, the supreme being/God of the universe, to be a guardian of Middle-earth. Gandalf was the only Istari (wizard) to actively pursue his role as a guardian, and so when he died, Ilúvatar resurrected him and sent him back so that he could aid in the campaign to defeat Sauron.

Gandalf has been featured in radio, television, stage, video game, music, and film adaptations, including Ralph Bakshis 1978 animated film. His best-known portrayal is by Ian McKellen in Peter Jacksons 2001–2003 The Lord of the Rings film series, where the actor based his acclaimed performance on Tolkien himself. McKellen reprised the role in Jacksons 2012–2014 film series The Hobbit.