Númenor is the fictional island kingdom that J.R.R. Tolkien described as the home of Aragorn’s ancestors.
Númenor is a great island realm created for Men who aided the Elves during the wars against Morgoth. Its people receive unusually long lifespans, and their kings descend from Elros, the half-elven brother of Elrond. Aragorn belongs to this royal line through the Dúnedain of the North.
The kingdom eventually falls because its rulers become envious of the immortal Elves and fear death. Under Ar-Pharazôn, Númenor attacks Aman, violating the ban imposed by the Valar. The island is then destroyed and submerged, while faithful survivors establish the realms of Arnor and Gondor in Middle-earth. Númenor is therefore a historical ancestor of both Aragorn’s lineage and the kingdoms he later unites.