Adûnaic (or Númenórean) ("language of the West") is one of the fictional languages devised by J. R. R. Tolkien for his fantasy works.

One of the languages of Arda in Tolkien's Middle-earth legendarium, Adûnaic was spoken by the Men of Númenor during the Second Age. By the time of the War of the Ring at the end of the Third Age, it had developed into the common speech or Westron.

Adûnaic was invented by the first Men as they awoke in Hildórien. It was the language of Númenor, and after its destruction in the Akallabêth, the "native speech" of the people of Elendil in the kingdoms of Arnor and Gondor in the west of Middle-earth, though they usually spoke the Elvish language Sindarin. By the time of the War of the Ring, it had developed into the common speech or Westron. Tolkien called Adûnaic "the language of the culturally and politically influential Númenóreans."

Although Tolkien created very few original words in Adûnaic, mostly names, the language serves his concept as the ancestor of a lingua franca for Middle-earth, Westron, a shared language for many different peoples.

Tolkien devised Adûnaic (or Númenórean), the language spoken in Númenor, shortly after World War II, and thus at about the time he completed The Lord of the Rings, but before he wrote the linguistic background information of the Appendices. Adûnaic is intended as the language from which Westron (also called Adûni) is derived. This added a depth of historical development to the Mannish languages. Adûnaic was intended to have a "faintly Semitic flavour". Its development began with his 1945 work The Notion Club Papers. It is there that the most extensive sample of the language is found, revealed to one of the (modern-day) protagonists, Lowdham, in a visionary dream of Atlantis. Its grammar is sketched in the unfinished "Lowdham's Report on the Adunaic Language", included in Sauron Defeated.

Tolkien remained undecided whether the language of the Men of Númenor should be derived from the original Mannish language (as in Adûnaic), or if it should be derived from "the Elvish Noldorin" (i.e. Quenya) instead. In The Lost Road and Other Writings it is implied that the Númenóreans spoke Quenya, and that Sauron, hating all things Elvish, taught the Númenóreans the old Mannish tongue they themselves had forgotten.

The phonology is as follows:

¹Adûnaic is fundamentally a three-vowel language, with a length distinction; the long eː and oː are derived from diphthongs aj and aw, as is the case in Hebrew and in most Arabic dialects, in line with the Semitic flavour that Tolkien intended for both Adûnaic and Khuzdul, which influenced it.