A palantír ([paˈlanˌtiːr]; pl. palantíri) is one of several indestructible crystal balls from J. R. R. Tolkien's epic-fantasy novel The Lord of the Rings. The word comes from Quenya palan 'far', and tir 'watch over'. The palantírs were used for communication and to see events in other parts of Arda, or in the past.

The palantírs were made by the Elves of Valinor in the First Age, as told in The Silmarillion. By the time of The Lord of the Rings at the end of the Third Age, a few palantírs remained in use. They are used in some climactic scenes by major characters: Sauron, Saruman, Denethor the Steward of Gondor, and two members of the Company of the Ring: Aragorn and Pippin.

A major theme of palantír usage is that while the stones show real objects or events, those using the stones had to "possess great strength of will and of mind" to direct the stone's gaze to its full capability. The stones were an unreliable guide to action, since what was not shown could be more important than what was selectively presented. A risk lay in the fact that users with sufficient power could choose what to show and what to conceal to other stones: in The Lord of the Rings, a palantír has fallen into the Enemy's hands, making the usefulness of all other existing stones questionable.

Commentators such as the Tolkien scholar Paul Kocher note the hand of providence in their usage, while Joseph Pearce compares Sauron's use of the stones to broadcast wartime propaganda. Tom Shippey suggests that the message is that "speculation", looking into any sort of magic mirror (Latin: speculum) or stone to see the future, rather than trusting in providence, leads to error.

In Tolkien's fantasy The Lord of the Rings, the palantírs were made by the Elves of Valinor in the Uttermost West, by the Noldor, apparently by Fëanor himself from silima, "that which shines". The number that he made is not stated, but there were at least eight of them. Seven of the stones given to Amandil of Númenor during the Second Age were saved by his son Elendil; he took them with him to Middle-earth, while at least the Master-stone remained behind.

Four were taken to Gondor, while three stayed in Arnor. Originally, the stones of Arnor were at Elostirion in the Tower Hills, Amon Sul (Weathertop), and Annuminas: the Elostirion stone, Elendil's own, looked only Westwards from Middle-earth across the ocean to the Master-stone at the Tower of Avallonë upon Eressëa, an island off Valinor. The stones of Gondor were in Orthanc, Minas Tirith, Osgiliath, and Minas Ithil.

By the time of The Lord of the Rings, the stone of Orthanc was in the hands of the wizard Saruman, while the stone of Minas Ithil (by then Minas Morgul, the city of the Nazgûl) had been taken by the dark lord Sauron. That of Minas Tirith remained in the hands of the Steward of Gondor, Denethor. The stone of Osgiliath had been lost in the Anduin when the city was sacked. Gandalf names two of these as the Orthanc-stone and the Ithil-stone.

A single palantír enabled its user to see places far off, or events in the past. A person could look into a palantír to communicate with anyone looking into another palantír. They could then see "visions of the things in the mind" of the person looking into the other stone.