Thargelion was a region of Beleriand, east of the river Gelion. It was north of the river Ascar, and therefore not counted as part of Ossiriand.
After the Rebellion of the Noldor this was the land of Caranthir, one of the Sons of Fëanor, and after him it was often called Dor Caranthir.
The Haladin briefly dwelt here until they were nearly wiped out in an Orc-raid.
Thargelion is a Sindarin name, consising of thar- ("across, over") +
- ↑ J.R.R. Tolkien, "Words, Phrases and Passages in Various Tongues in The Lord of the Rings", in Parma Eldalamberon XVII (edited by Christopher Gilson), p. 34