Pasighat is the headquarters of East Siang district in the Indian state of Arunachal Pradesh. Situated at the eastern foothills of the Himalayas at 155 metres (509 ft) above mean sea level, Pasighat is Arunachal's oldest town. The Government of India included Pasighat in the Smart Cities Mission development scheme in June 2017.

It hosts an Advance Landing Ground (ALG) of Indian Air Force.

The site of present-day Pasighat was known to the Adi people before British contact as Paklek (also Paglek), a name understood to derive from the Adi word for banana (kopak), with the settlement taking its present name from the Pasi, one of the Adi sub-tribes who were among its earliest inhabitants. Before the Pasi and other Adi communities settled the foothills around the Siang River, the area had earlier been inhabited by Dibu-Marang clans, whose displacement by incoming Adi groups is recorded in local oral tradition.

Pasighat was formally founded in 1911 by the British Raj as a gateway to administrative convenience of the greater Abor Hills and the north area in general. Primarily, there were settlements of Adi tribesmen, who are still living in the villages in and around Pasighat. Cognizance of Pasighat emerged due to the last Anglo-Abor War that was fought in 1912 subsequent to the fourth Anglo-Abor War in 1894. This necessitated the first-ever administrative headquarters being established here with an Assistant Political Officer posted. T. E. Furze, an Imperial Police officer, was the first Assistant Political Officer appointed to Pasighat, taking up the post in 1912. In its earliest years, small trading shops run by Marwari and Bihari merchants brought by the British from Sadiya served the needs of the administration, and Nepali porters who arrived with British columns from the 1930s onward formed another strand of the town's early population.

Under the Government of India Act 1919, the frontier tracts were placed under the direct authority of the Governor of Assam and declared Backward Tracts. The Government of India Act 1935 renamed them Excluded Areas in 1936, placing them outside the legislative competence of the Assam assembly. Between 1943 and 1948 the tracts were reorganised into five agencies: Sela, Subansiri, Abor, Mishmi and Tirap, with Pasighat remaining the seat of the Abor subdivision throughout.

Among the officers who served as Assistant Political Officer at Pasighat during the British period, Peter Loren Seton James was the last. He was known to the Adi communities of the Siang valley by several names: Jam Haap, an informal rendering of his surname; Jame Sab, from the Hindustani sahab; and Jame Migom, the name used by communities further up the river. He spoke Adi fluently, lived alongside the people he administered when on tour, and was recognised as an authority on Moshup Abang, a traditional form of Adi oral verse. He was also known to take the role of miri, the lead performer, in the ponnung ceremonial dance, a level of participation unusual for a colonial officer. As independence approached, the colonial administration arrested the Congress organiser Moje Riba and others at Pasighat in response to nationalist activity in the frontier tracts; James was subsequently removed from his post and those detained were released. On 15 August 1947, Riba hoisted the Indian national flag at Dipa village, the first such ceremony in the region. James formally handed the Abor Hills district to the Government of India in September 1948, delivering a farewell address to the Adi communities urging them to preserve their culture and to invest in the education of their children.

In the post-independence era, Pasighat is credited with the first Airfield (near Paglek, P. I. Line) established in 1946. The original market area of the town, which lay closer to the Siang River, was washed away by flooding, and the present market was established in 1955. Road connections from Pasighat to Jonai, to Mebo, to Oryamghat and to Along were built from 1963, and electricity reached the town in 1975. The first Agricultural Institute in Arunachal Pradesh was also established at Pasighat in 1950. Other forms of later infrastructural development include:

Early proponents for moving the state capital from Shillong (the then NEFA), underlined Pasighat's better infrastructure. However, the privilege was lost to the present capital Itanagar in 1974. The only significant development in Pasighat that came after that was the College Of Horticulture and Forestry Central Agriculture University established on 7 March 2001.