The Barharwa–Azimganj–Katwa loop is a railway line connecting Barharwa on the Sahibganj loop and Katwa. Together with the Bandel–Katwa line, which connects this line to Bandel Junction on the Howrah–Bardhaman main line, it is also known as the B.B Loop Line. This 170 kilometres (110 mi) line is under the jurisdiction of Eastern Railway. The majority of this line passes through the Purba Bardhaman and Murshidabad districts, in the Indian state of West Bengal, and lies on the west bank of the Bhagirathi river.

The Sahibganj loop is a railway line connecting Khana Junction and Kiul Junction. Originally a part of the Howrah–Delhi main line, it was opened to traffic in 1866. With the construction of a shorter railway line for a part of the route, the 403.8 kilometres (250.9 mi) stretch was assigned a separate identity.