The District of Lower Subansiri, which is lying approx between 92º40′ and 94°21′ East Longitude and 26°55″ and 28°21′ North Latitudes, covers an area of 3,460 (approx) Sq.km., is bounded on the North by Kurung-Kumey and Upper Subansiri Districts of Arunachal; on the South by Papum Pare District of Arunachal Pradesh and Assam ; on the East by West Siang and some part of Upper Subansiri ; and on the West by Kurung-Kumey and Papumpare Districts of Arunachal Pradesh. The altitude of Lower Subansiri district headquarters is 1500 meters above sea level.
The district was formed when Subansiri district was bifurcated into Upper and Lower Subansiri districts in 1987. Lower Subansiri district has a long ancient history related with the Chutiya Kingdom. It was probably under Chutiya chieftain rule from a long time, and came under Birpal’s rule in the 12th century. In 1999 Papum Pare district was split to form new district, and this was repeated on 1 April 2001, with the creation of Kurung Kumey district.
In October 2017 the state government approved the creation of Kamle district, involving the carving out of Raga, Dolungmukh and Kumpurijio circles from Lower Subansiri district.
According to the 2011 census Lower Subansiri district has a population of 82,839, roughly equal to the nation of Andorra. This gives it a ranking of 623rd in India (out of a total of 640). The district has a population density of 24 inhabitants per square kilometre (62/sq mi) . Its population growth rate over the decade 2001–2011 was 48.65%. Lower Subansiri has a sex ratio of 975 females for every 1000 males, and a literacy rate of 76.33%.
This district is inhabited by Nyishis and Apatanis.