An eastern segment of the wide woodlands that made up the land of Doriath in central Beleriand, Arthórien was a part of the great forest of Region, separated from the rest of that forest by the river Aros. It thus formed an eastern march or borderland of Doriath between the rivers Aros and Celon, whose course ran nearly parallel to Aros, but father to the east. Eastward of Celon, the dense woods of Doriath gave way to the wide plains of East Beleriand.

After the return of Morgoth to Middle-earth, the Dark Lord sent his Orcs against the Elves, and there was fighting across Beleriand. The Green-elves of Ossiriand - far to the east and south of Doriath - had little defence against this sudden assault, and their lord Denethor was slain in battle. Many of the survivors sought refuge within Doriath, and they settled in the woods of Arthórien. There, they were safe within the Girdle of Melian, an impassable magical boundary that ran along the course of Celon, marking Arthórien's eastern border with the wilds beyond. Among these refugees was a haughty Elf named Saeros, who would later rise in the court of King Thingol, and whose accidental slaying would lead to the exile of Túrin from the kingdom.