The fictional island kingdom ruled by Ar-Pharazôn in J.R.R. Tolkien’s legendarium is Númenor.
Númenor is an island realm given to the Edain after the wars against Morgoth at the end of the First Age. Its people, the Númenóreans, receive long life and great knowledge, though they remain mortal. The kingdom lies in the sea between Middle-earth and Aman.
Ar-Pharazôn becomes Númenor’s final king after seizing the throne from his cousin Tar-Míriel. Influenced by Sauron, he attempts to challenge the Valar and land in Aman, seeking immortality. This rebellion leads to the island’s destruction and the reshaping of the world. Númenor’s surviving faithful establish the realms of Arnor and Gondor in Middle-earth.