Gwaihir is the great eagle who rescues Gandalf from Isengard in Tolkien’s stories.
Gwaihir the Windlord carries Gandalf away from the summit of Orthanc after Saruman imprisons him there. In The Lord of the Rings, Gwaihir also carries Gandalf after his battle with the Balrog and later helps transport Gandalf and the wounded Frodo and Sam from Mount Doom.
Gwaihir belongs to the race of Great Eagles, intelligent and powerful beings associated with the mountains of Middle-earth. He is not a normal animal mount and does not simply obey every request from the peoples of Middle-earth.
Readers sometimes confuse Gwaihir with Thorondor, another major Eagle. Thorondor is the lord of the Eagles in the First Age, while Gwaihir appears prominently in the events of The Hobbit and The Lord of the Rings.