The fictional language associated with Mordor’s forces in J.R.R. Tolkien’s works is the Black Speech.
Tolkien describes the Black Speech as a language created by Sauron during the Second Age for the servants of his realm. Its most famous surviving example is the inscription on the One Ring: “Ash nazg durbatulûk, ash nazg gimbatul,” followed by lines describing one Ring ruling the others. The inscription appears in the language on the Ring rather than in one of the Elvish tongues.
Black Speech is often confused with Orcish, but Tolkien did not present every language used by Orcs as a single fully developed tongue. The Black Speech was Sauron’s deliberate attempt to impose a common language on his followers. Quenya and Sindarin are Elvish languages, while Westron is the Common Speech used widely by the peoples of Middle-earth.