Númenor is the fictional island kingdom that J.R.R. Tolkien describes as a homeland of Men in the Second Age.
The island was raised from the sea by the Valar as a reward for the Men who fought alongside the Elves during the War of Wrath. Its people, the Númenóreans, enjoyed unusually long lives and developed a powerful maritime civilization. Elros, brother of Elrond, became the first king of Númenor.
Númenor’s history ends in catastrophe when its king, Ar-Pharazôn, attempts to challenge the Valar and seize immortality. The island is destroyed and submerged, while faithful survivors reach Middle-earth and establish kingdoms including Gondor and Arnor.
Númenor is distinct from Gondor, which was founded later in Middle-earth, and from Aman, the realm across the sea. Tolkien’s account of the island appears most fully in The Silmarillion and related writings.