What event destroyed Númenor in J.R.R. Tolkien’s legendarium?

The event that destroyed Númenor in J.R.R. Tolkien’s legendarium is called the Downfall of Númenor.

Númenor was a powerful island kingdom inhabited by Men who had been rewarded after the First Age. Over time, fear of death and resentment toward the immortal Elves grew among its rulers. King Ar-Pharazôn eventually challenged the Valar and sailed west to attack the Undying Lands.

The rebellion ended catastrophically. Eru Ilúvatar changed the shape of the world, Númenor was overwhelmed by the sea, and the surviving Faithful escaped to Middle-earth under Elendil. Tolkien presents the Downfall as a mythic account of pride, mortality, power, and divine judgment.

The event is sometimes confused with the War of Wrath, which ended the First Age and destroyed much of Beleriand. The Downfall occurred later, near the end of the Second Age. Its survivors founded the realms of Arnor and Gondor, linking Númenor’s history directly to The Lord of the Rings.