Dibang River is a tributary river of the Brahmaputra that flows through the northeast Indian states of Arunachal Pradesh and Assam.
The Dibang originates near Keya pass on the Indo-Chinese border in the Dibang Valley district of Arunachal Pradesh. The drainage basin of the river within Arunachal Pradesh covers the districts of Dibang Valley and Lower Dibang Valley. The Mishmi Hills lie in the upper course of the Dibang which enters the plains at Nizamghat. Between Nizamghat and Sadiya the Dibang has a steep river gradient and exhibits braided channel morphology with its width varying from 4 to 9 kilometres (2 to 6 mi). It often changes its course resulting in flooding and destruction of cultivable land and forests along its banks. The Dibang, with a total length of 195 kilometres (121 mi), enters the River Lohit north of the Dibru-Saikhowa sanctuary near the Assamese town of Sadiya.
The Mathun, Tangon, Dri, Ithun and Emra are the major tributaries of the Dibang. The Dibang is also joined by a number of tributaries such as the Airi Pani, Ilu Pani, Imu Pani, Ahi, Ashupani, Epipani and Deopani rivers during its course. Most of these rivers join it in the upper course in the hills thus giving it a wide fan shaped catchment region.
In 2008 Prime Minister Manmohan Singh laid the foundation stone for a 3000 MW dam as part of the Dibang Multipurpose Project the district of Lower Dibang Valley. Seventeen other dams with power potential between 20 and 4500 MW have also been proposed for the Dibang. The proposed Dibang dam, at 288 metres (945 ft), on completion would be among the largest dams in India and among the world's tallest gravity dams has since run into opposition from the Mishmi people and the Assamese who live downstream of the project.