Diffo Bridge is a pre-stressed concrete box girder bridge over the Diffo river (Chipu river) ^[3] in Arunachal Pradesh, India. This 426.60 metres (1,399.6 ft) long bridge was inaugurated in 2019 by the Union Defense Minister Nirmala Sitharaman. ^{[2] [4]}

The construction started in 2011 ^[4] by Border Roads Organisation under Project Udayak. ^[4] It was built for an estimated cost of ₹4,847.83 lakh (US$5.8 million), which was funded by the Union Ministry of Road Transport and Highways. ^[2] Tough working conditions in an inhospitable terrain facing turbulent flash floods, made construction difficult. It was completed in 8 years. ^[2] The bridge was inaugurated by the Union Defense Minister Nirmala Sitharaman on 18 January 2019. ^[2]

Earlier, Indian Defense Forces had laid the Bailey bridge over the Diffo River. It was a temporary structure that had to be closed during most rains. ^[5] The new bridge provides uninterrupted access between Dibang Valley and Lohit valley of Eastern Arunachal Pradesh on Roing-Koron-Paya Road. ^[4] Lohit valley is the corridor that leads to Kibithu, the battleground of the 1962 Indo-Sino war and Lower Dibang Valley leads to the Anini front of border with China. ^[5] The bridge reduced traveling time between Tezu and Roing (district headquarters of Lohit Valley and Lower Dibang Valley respectively) from 3 hours to 45 minutes. During a monsoon, the old route took travelers through Assam. ^[5] Strategically, it provides an all-weather route for troops deployed on the China border ( the McMahon line). ^[6]