Eagles were the greatest and the most beautiful of all birds. Manwë created them in the First Age before the Children of Ilúvatar were awakened as lords of the living creatures. Eagles were bound to help Elves and Men in the war against Melkor Morgoth. In the First Age they were ruled by Thorondor, the largest of all eagles with a wingspan of 180 feet across, and they nested in the Crissaegrim. The eagles protected the hidden city of Gondolin from the spies of Morgoth, in the First Age, rescued the lovers Beren and Lúthien from Morgoth's stronghold of Angband, and defeated many dragons in the Great Battle of the War of Wrath.

The eagles seemed to have vanished in the Second Age, perhaps to Valinor. They returned to warn the Númenórians of the imminent destruction of Númenor.

In the Third Age the eagles were led by Gwaihir the Windlord, and aided in many battles and helped many people. They saved the Elves, Men, and Dwarves from defeat in the Battle of Five Armies, helped Gandalf escape from Orthanc, and rescued Frodo and Samwise from the slopes of Mount Doom after the destruction of the One.

Eagles were very large, large enough to easily carry a man, and lived very long lives. They may have been immortal. They could speak Westron, and the languages of Men and Elves. They were sometimes called, because of their size and heroic deeds, the Great Eagles. They exist no more, only their smaller relatives now survive.