In J.R.R. Tolkien’s legendarium, what language is used for the One Ring’s inscription?

The One Ring’s inscription in J.R.R. Tolkien’s legendarium is written in the Black Speech of Mordor.

The inscription begins “Ash nazg durbatulûk” and describes the Ring’s power over the other Rings of Power. The full couplet is part of the verse recited by Gandalf when he explains the Ring’s history to Frodo in The Fellowship of the Ring.

Tolkien described the Black Speech as a language created by Sauron for the servants of Mordor. Unlike Quenya and Sindarin, it is not an Elvish language. The inscription is especially associated with the Ring’s fiery letters, which become visible when it is heated.

The language is sometimes incorrectly called Mordor’s Elvish or confused with Orcish. Tolkien’s writings treat these as distinct concepts, and the inscription’s words are specifically identified with the Black Speech.