The Barauni–Guwahati railway line connects Barauni, Saharsa, Purnia and Katihar in the Indian state of Bihar and Bongaigaon, Kamakhya and Guwahati in Assam via Siliguri, Jalpaiguri, Cooch Behar and Alipurduar in West Bengal.

The 784 km (487 mi)-long trunk line, been treated in more detail in smaller sections: The earliest railway tracks in Assam were laid in the Dibrugarh area in 1882 for the transportation of tea and coal.

During the 1900–1910 period, the Eastern Bengal Railway built the Golakganj–Amingaon branch line, thus connecting the western bank of the Brahmaputra to Bihar and the rest of India.

The construction of the 2.025 km (1.258 mi)-long Rajendra Setu near Barauni in 1959 provided the first opportunity to link the railway tracks on the north and south banks of the Ganges.

Jawaharlal Nehru, India's first prime minister formally laid the foundation stone on 10 January 1960 and it was completed in 1962, connecting the two parts of the metre-gauge railways in Assam.

The bridge named after Coochbehar King Sri Naranarayan Koch (Rajbangsi) Maharaj falls in 182.9 km (113.6 mi) long New Bongaigaon - Goalpara Town - Guwahati Railway line.

[14] As of July 2021, Katihar - Srirampur Assam and Bongaigaon Kamakhya section has been electrified, and many electric passenger trains are going up to NCB.