Which is the longest National Highway in India?

India's National Highways (NHs) are numbered by the Ministry of Road Transport & Highways, and a highway's number has no fixed relationship with its length. During the 2010 renumbering exercise, several older, separately-numbered highways were joined end-to-end into single, continuous corridors spanning multiple states.

Comparing the documented route length of each of the four given highways:

• NH 5 (old numbering): about 1,533 km, through Tamil Nadu, Andhra Pradesh, and Odisha, connecting Chennai to Jharpokharia in Odisha.

• NH 44: about 3,745 km, through Jammu & Kashmir, Himachal Pradesh, Punjab, Haryana, Delhi, Uttar Pradesh, Rajasthan, Madhya Pradesh, Maharashtra, Telangana, Andhra Pradesh, Karnataka, and Tamil Nadu, connecting Srinagar to Kanyakumari — formed by merging several pre-2010 highways, including the historic NH 7, into one continuous corridor.

• NH 10 (old numbering): about 403 km, through Delhi, Haryana, and Punjab, connecting Delhi to Fazilka.

• NH 15 (old numbering): about 1,526 km, through Punjab, Rajasthan, and Gujarat, connecting Pathankot to Samakhiali.

Comparing these documented lengths, NH 44's approximately 3,745 km is, by a wide margin, the greatest of the four — making it the longest National Highway in India.