Harfalas was the southern half of the region of Falas, located southeast of Eglamar, and northwest of Arvernien.
The region of Harfalas was marked on the Second 'Silmarillion' Map, which formed the basis for the map of Beleriand in the published Silmarillion.
However, apart from being labeled on the aforementioned map, Harfalas was never mentioned again, nor did it appear in any of the narratives, annals or essays set in the First Age.