Arunachal Pradesh (, lit. 'Land of Dawn-Lit Mountains') is a state in Northeastern India. It was formed from the erstwhile North-East Frontier Agency (NEFA) region, and became a state on 20 February 1987. It borders the states of Assam and Nagaland to the south. It shares international borders with Bhutan in the west, Myanmar in the east, and a disputed border with China in the north at the McMahon Line. Itanagar is the state capital of Arunachal Pradesh. Arunachal Pradesh is the largest of the Seven Sister States of Northeast India by area. Arunachal Pradesh shares a 1,129 km border with China's Tibet Autonomous Region.As of the 2011 Census of India, Arunachal Pradesh has a population of 1,382,611 and an area of 83,743 square kilometres (32,333 sq mi). It is an ethnically diverse state, with predominantly Monpa people in the west, Tani people in the centre, Mishmi and Tai people in the east, and Naga people in the southeast of the state. About 26 major tribes and 100 sub-tribes live in the state. The main tribes of the state are Adi, Nyshi, Singpho, Galo, Tagin, Apatani, and so forth. The Mishmi tribe has three sub-tribes, namely Idu-Mishmi, Digaru-Mishmi and Miju-Mishmi. A major part of the state is claimed by both the People's Republic of China and the Republic of China as part of the region of South Tibet. During the 1962 Sino-Indian War, most of Arunachal Pradesh was captured and temporarily controlled by the Chinese People's Liberation Army.

The Lower Dibang Valley district (Pron:/dɪˈbæŋ/) is an administrative district in the state of Arunachal Pradesh in northeastern India. It is the tenth least populous district in the country.