The Reunited Kingdom was the realm ruled by Elessar and those of the house of Telcontar who succeeded him. It was so called because it included all the lands of both Gondor and Arnor, claimed by Elendil and divided after his death.

The capitals of the Reunited Kingdom were Annúminas and Minas Tirith.

At the beginning of the Fourth Age, the Reunited Kingdom included all those lands that were part of Arnor and Gondor at their greatest extent, except for Rohan and the Shire.

In addition, the King of the Reunited Kingdom was overlord of Dale and Erebor, and probably received tribute from much of Harad and Rhûn.