The Mahananda (/məˌhɑːˈnʌndə, ˌmɑːhə-/ mə-HAH-NUN-də, MAH-hə-) is a trans-boundary river that flows through the Indian states of Bihar and West Bengal before crossing into Bangladesh.

[1] The Fulahar originates in the Himalayas in Nepal and traverses through the Indian state of Bihar and merges with the Ganges in left opposite to Rajmahal.

[2] The Mahananda originates in the Himalayas: Paglajhora Falls on Mahaldiram Hill near Chimli, east of Kurseong in Darjeeling district at an elevation of 2,100 metres (6,900 ft).

It is low-lying and vulnerable to inundation during rainy season; the southern area consists of very fertile land and is thickly populated, being commonly known as "Diara".

[3] The main tributaries of the Mahananda are Balason, Mechi, Kankai[3] and River Kalindri.