View of Arun River from Leguwa VDC of Nepal.
|- left||Yeru Tsanpo, Trakar-chu|
|- right||Barun River|
|Mouth||Joins with Sun Kosi and Tamur River to form Sapta Kosi|
|- location||Tribenighat, Nepal|
The Arun River (Nepali: अरुण नदी) is a river that flows from Tibet to Nepal. It is a part of Koshi River which flows into India. It is known as Phung Chu or Bum-chu at Tibet, from where it starts. Around 37 percent of the total water of Koshi River comes from this river.