Númenor is the great island kingdom founded for the Edain in J.R.R. Tolkien’s Second Age.
The Edain were Men who had aided the Elves during the wars against Morgoth in the First Age. As a reward, the Valar granted them a new island in the Great Sea, closer to Valinor than to Middle-earth. The kingdom was also called Westernesse.
The first king was Elros Tar-Minyatur, the half-elven brother of Elrond. Elros chose the fate of Men and founded the Númenórean royal line. His descendants ruled an increasingly powerful maritime civilization for centuries.
Númenor’s people were forbidden to sail west to the Undying Lands, but they were allowed to look toward them. Their eventual rebellion against the Ban of the Valar led to the island’s destruction. Elendil and other survivors later established kingdoms in Middle-earth.