The Mirror of Erised is a magical object which is prominently featured in the first Harry Potter novel, Harry Potter and the Philosopher's Stone (released in the United States as Harry Potter and the Sorcerer's Stone). The name of the object is actually a clever pun, as the mirror image of “erised” is, of course, desire. The Mirror of Desire reflects the most profound wish of the person who is standing in front of it, showing him or her sublimely happy.

Readers are first introduced to the Mirror of Erised when Harry Potter encounters it stored in a side room while fleeing Argus Filch. The frame of the mirror bears the words “erised stra ehru oyt ube cafru oyt on wohsi,” which when reversed read “I show not your face but your heart's desire.” Harry Potter looks into the Mirror of Erised and sees his parents and family, stretching back for many generations. When he takes his friend Ron back to the room to look into the mirror, Ron sees himself as a highly successful Hogwarts student, holding the position of Head Boy and being praised by his family.

Although Harry does not understand how the Mirror of Erised works, he becomes obsessed with it and returns night after night. Albus Dumbledore becomes aware of this, and appears one night to tell Harry that the mirror is being moved, and that he should not look for it. Dumbledore also clarifies what the Mirror of Erised does, telling Harry that the mirror does not predict the future or reflect reality, but rather the desires of the viewer. When Harry asks Dumbledore what he sees, Dumbledore says that he sees himself holding a pair of socks, which may not be strictly true.

The Mirror of Erised returns at the end of the book as the last challenge in a series of puzzles which are used to protect the Philosopher's Stone. Dumbledore enchants the Mirror of Erised so that it will give the stone to someone who wants to find the stone, but not use it. When Harry looks into the mirror, the stone appears in his pocket.

Although the Mirror of Erised is infrequently mentioned after the first book, it may still play a role in the Harry Potter books, assuming that it has not been destroyed. It also provides an important object lesson in the book, because in addition to reflecting desires, the mirror also provides clues into the nature of the person looking into it. Harry, the hero, has noble desires with which readers can sympathize. Voldemort, who is portrayed as greedy and selfish, is unable to unlock the key of the mirror and get the Philosopher's Stone, suggesting that it can only be held by the righteous.