In J. R. R. Tolkien's fictional world of Middle-earth, the Ring-inscription is a Black Speech inscription in Tengwar upon the One Ring, symbolising the Ring's power to control the other Rings of Power.

Normally the One Ring appears perfectly plain and featureless, but when heated in a fire the inscription appears in fiery letters inside and outside the Ring. A drawing of the Inscription appears in Book I, Chapter 2 of The Fellowship of the Ring, "The Shadow of the Past". A transliteration appears in Book II, Chapter 2, "The Council of Elrond", where the inscription is read by Gandalf (One Ring inscription.ogg):

Ash nazg durbatulûk, ash nazg gimbatul, ash nazg thrakatulûk, agh burzum-ishi krimpatul

These words, in the Black Speech of Mordor, are physically painful to any Elf who hears them. It seems that the inscription uses Elvish lettering because the other Rings of Power were made by the Elves.

Roughly translated, they mean:

One Ring to rule them all, One Ring to find them, One Ring to bring them all, and in the darkness bind them

Note: some recent editions of The Fellowship of the Ring accidentally omit the first two clauses of this phrase from Chapter 2.

The entire poem reads:

Three Rings for the Elven-kings under the sky,

Seven for the Dwarf-lords in their halls of stone,

Nine for Mortal Men doomed to die,

One for the Dark Lord on his dark throne

In the Land of Mordor where the Shadows lie.

One Ring to rule them all, One Ring to find them,

One Ring to bring them all, and in the darkness bind them,

In the Land of Mordor where the Shadows lie.

Gandalf first learned of the Ring-inscription when he read the account that Isildur had written before marching north to his death and the loss of the Ring. When Isildur had cut the ring from Sauron's hand, it was burning hot, and so Isildur was able to transcribe the inscription before it faded.

When Gandalf subsequently heated the ring that Bilbo Baggins had found and passed on to Frodo the inscription appeared, leaving him in no doubt that it was the One Ring.