From Tolkien Gateway
Arandor, also known as Kingsland, was the important central region of Númenor, around the island's capital at Armenelos between the Meneltarma near the centre of the island and the port of Rómenna on its eastern coast. It was almost landlocked, but it met the Sea in the far east, where the great port of Rómenna lay. From there, a road ran westward to Armenelos and then on to the Meneltarma on the western borders of Arandor.
In the Third Age, Arandor was also one of the alternate names for Arnor.