Lohit is an administrative district in the state of Arunachal Pradesh in India. The district headquarters are located at Tezu. As of 2011 it is the third most populous district of Arunachal Pradesh (out of 16), after Papum Pare and Changlang.

It was known earlier as the Mishmi Hills. The district is named after the Lohit River, from the Sanskrit Louhitya, reddish- or rust-coloured, and consists of the river valley and hills/mountains to the North and South.

During the medieval times, the present district was under the control of the rulers of the Sutiya Kingdom. The Sutiya rulers controlled the area from early 13th century to the 16th century and during the 19th century it became one of the last territories to be brought under British control after the punitive Abor and Mishmi Expedition in the first decade of 20th century.

In June 1980, Dibang Valley district was split from Lohit (and has since been bifurcated again to create the new Lower Dibang Valley district).On 16 February 2004, Anjaw district was carved out from the northern part of Lohit district bordering Tibet and Myanmar, with its headquarters at Hawai. Anjaw was carved out under the Arunachal Pradesh Re-organization of Districts Amendment Bill.

Namsai is an important sub-division of this district. It is a disyllabic word originated from the local dialect khampti: Nam means water and sai means sand. The place is so called because it is situated on the bank of the river Dihing, which is a tributary of Brahmaputra. Namsai, India connects with Tinsukia district of Assam. Lohit district occupies an area of 11,402 km² and has a population of 143,478 (as of 2001).

The area is highly inaccessible, and it was only in 2004 that a permanent bridge has been made operational across the Lohit at the holy site of Parashuram Kund, giving round-the-year connection to Tezu. East of Tezu (about 100 km) lies the small town of Hayuliang, and this is slated to become the headquarters of a new district. The road along the Lohit runs right up to the small garrison town of Walong just south of the China border, site of the famous Battle of Walong in 1962.

Languages spoken include Galo, an endangered Sino-Tibetan tongue with 30 000 speakers, spoken in the eastern part of the district.

In 1989 Lohit district became home to the Kamlang Wildlife Sanctuary, which has an area of 783 km2 (302.3 sq mi).It is the home to some of the endangered flora and fauna. The district has been found to be an ideal place for Jatropha cultivation, which is used for bio-diesel making.