|Other names||Deadmen's Dike, Norbury of the Kings|
|Etymology||"Northern Fortress (of the) Kings"|
|Events||Fall of Fornost|
It is not known when Fornost was founded or when the kings of Arnor moved there from Annúminas, but it is known that the kings moved to Fornost some time before T.A. 861, when King Eärendur died, and Arnor was divided into three kingdoms with Fornost the capital of the greatest kingdom, Arthedain.
- Main article: Fall of Fornost
In T.A. 1974, Arthedain was overrun by the forces of Angmar. Fornost was captured, and King Arvedui fled into the northern wastes and was lost in the Icebay of Forochel. In the following year, a fleet of ships from Gondor, led by Eärnur, landed at Mithlond. Eärnur fought the Witch-king of Angmar in the plains west of Fornost and defeated the armies of Angmar, but the Witch-king himself escaped.
After Fornost Erain was abandoned, the inhabitants of the nearest settlement, Bree, referred to it as Deadman's Dike, and did not come there. Only Rangers came there from time to time, but no-one knew what they did there.
Fornost Erain is Sindarin. It means "Northern Fortress (of the) Kings"; from forn "north" and ost "fortress", and erain is the plural of aran. It was called "Norbury of the Kings" in Westron, a fitting translation.