The inscription on the One Ring in J.R.R. Tolkien’s works is written in the Black Speech of Mordor. Sauron created this language for the servants of Mordor and used it for the Ring inscription.
The inscription consists of two lines from the Ring-poem: “One Ring to rule them all, One Ring to find them; One Ring to bring them all and in the darkness bind them.” The words are written in Tengwar script, but the language itself is Black Speech. This distinction matters because script and language are not the same thing.
The Ring-poem refers to the Rings of Power made for Elves, Dwarves, and Men. The One Ring was designed to control the other Rings and strengthen Sauron’s power over their bearers.
Readers sometimes identify the inscription as Elvish because it uses Tengwar, a script associated with the Elves. Tolkien’s world allows different languages to be written in the same script, so the lettering does not determine the language being spoken.