Númenor is the fictional island kingdom destroyed in J.R.R. Tolkien’s history of Middle-earth. Its destruction is described in the account commonly called the Downfall of Númenor.
The island was granted to the Men who had aided the Elves during the wars against Morgoth. Númenor became a powerful maritime kingdom, but its people grew increasingly fearful of death and resentful of the immortal Elves. Under Ar-Pharazôn, the king, Númenor challenged the power of the Valar.
The island was finally overwhelmed and changed the shape of the world. Elendil and his sons escaped with the Faithful and founded the realms of Arnor and Gondor in Middle-earth. Númenor is sometimes confused with Beleriand, which was destroyed earlier in the First Age, or with Gondolin, a hidden city that also fell.