|Location||Flowing from Himlad around Doriath to the Sirion|
|Etymology||D. ar "bloody red"[source?]|
Aros was a river of East Beleriand that arose in the northern lands west of the Pass of Aglon in the Shadowy Spring. It flowed south between Dor Dínen and Himlad (between these two lands the river could be crossed at Arossiach). The river's course then followed the eastern and southern boundaries of the Forest of Region (and thus formed much of the border of the Kingdom of Doriath) before it met the Sirion at Aelin-uial. Its one main tributary was the River Celon.