The Mirror of Galadriel is the seventh chapter of the Book Two of The Fellowship of the Ring.
During their visit to Lothlórien, Frodo Baggins and Samwise Gamgee were invited by the Lady Galadriel to gaze into the Mirror. She told them that to some she could command the mirror to show what they desire to see, but that "the Mirror will also show things unbidden, and those are often stranger and more profitable," for the Mirror "shows things that were, and things that are, and things that yet may be." She offered both Frodo Baggins and Sam Gamgee the chance to look into the mirror, and they accepted. Sam saw a vision of Frodo asleep under a cliff, and of himself climbing an endless stair; he also saw Ted Sandyman cutting down trees and his "old gaffer" being expelled from his Hobbit-hole. Frodo saw a vision of a wizard who seemed to be Gandalf, but the figure was dressed in white and carried a white staff, so Frodo thought he might be mistaken and that it could be Saruman instead. He also had a glimpse of the sea and a black ship with a white fortress with seven towers. Then Frodo saw the Eye of Sauron and the heat of Sauron's gaze as he sought for Frodo, at which the water seemed to grow hot and steam began to rise from it.