Númenor is the fictional island kingdom that falls into the sea in J.R.R. Tolkien’s Akallabêth.
Númenor was an island realm granted to Men who had aided the Elves during the wars of the First Age. Its people became renowned for long life, maritime skill, and learning. Over time, however, fear of death and resentment toward the immortal Elves grew among many Númenóreans.
King Ar-Pharazôn eventually challenged the power of the Valar by sailing west with a great fleet. The island was destroyed, and the world was changed from flat to round in Tolkien’s mythic history. Elendil and his sons escaped the catastrophe and later founded the realms of Arnor and Gondor in Middle-earth.
Númenor is also called Westernesse and, in Tolkien’s languages, Anadûnê or Númenórë. It should not be confused with Beleriand, a First Age region that was also destroyed, but by a different cataclysm.