Númenor is the fictional island homeland of the Men in J.R.R. Tolkien’s Second Age. The island is raised from the sea by the Valar as a reward for the Edain who fought Morgoth in the First Age.
The Númenóreans receive long life and great knowledge, but they are forbidden to sail to the Undying Lands of Aman. Over time, fear of death and resentment of the ban grow among their rulers. Sauron eventually corrupts King Ar-Pharazôn and persuades him to attack the Valar.
The island is destroyed in the Downfall of Númenor, an event Tolkien presents as a reshaping of the world. Elendil and his sons survive and establish the kingdoms of Arnor and Gondor in Middle-earth. Númenor is therefore the ancestral source of the royal line that later includes Aragorn.