Lower Subansiri district is one of the 17 administrative districts of the state of Arunachal Pradesh in northeastern India.

The district was formed when Subansiri district was bifurcated into Upper and Lower Subansiri districts in 1987.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.

The district headquarters are located at Ziro. The district occupies an area of 3,460 km²

It is bounded on the north by the Upper Subansiri district 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 East Kameng district of Arunachal Pradesh.

Languages used in the district include Apatani, Nyishi language.

Major local festivals of the district are Nyokum, Boori-Boot and Dree Festival.

There are 6 administrative circles in this district, namely, Ziro (Sadar), Yachuli, Pistana, Raga, Kamporijo and Dollungmukh. The district also divided into 3 blocks: Ziro-I, Ziro-II and Tamen-Raga.

There are 2 Arunachal Pradesh Legislative Assembly constituencies located in this district: Yachuli and Ziro-Hapoli. Both of these are part of Arunachal West Lok Sabha constituency