Thargelion was the name given by the Noldor to the region that lay between the River Gelion, East Beleriand, the Blue Mountains, Mount Rerir and the Ascar.

It had previously been known by the Grey-elves as Talath Rhúnem, the East Vale.

The region was taken by Caranthir after the return of the Noldor. It subsequently became known as Dor Caranthir. At that time, Thargelion became the main place through which the Dwarves of the Blue Mountains came to trade with Beleriand.

After the Nirnaeth Arnoediad, Morgoth and his armies took the region.