|State||West Bengal, Bihar|
|Cities||Siliguri, Ingraj Bazar|
|- location||Godagiri, Nawabganj District, Bangladesh|
|Length||360 km (220 mi)|
|- left||Tangon River, Nagar River (Rangpur)|
|- right||Mechi River, Kankai River, Balason River, Kalindri River|
The Mahananda River (Pron:/ˌməhɑːˈnʌndə or ˌmɑːhəˈnʌndə/) (Nepali: महानदी, Hindi: महानन्दा नदी, Bengali: মহানন্দা নদী) is a trans-boundary river that flows through the Indian states of West Bengal and Bihar, and Bangladesh.
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 flows through Mahananda Wildlife Sanctuary and descends to the plains near Siliguri. It touches Jalpaiguri district.
It enters Bangladesh near Tentulia in Panchagarh District, flows for 3 kilometres (1.9 mi) after Tentulia and returns to India. After flowing through Uttar Dinajpur district in West Bengal and Kishanganj and Katihar districts in Bihar, it enters Malda district in West Bengal. The Mahananda divides the district into two regions — the eastern region, consisting mainly of old alluvial and relatively infertile soil is commonly known as Barind (Borendrovomee), and the western region, which is further subdivided by the river Kalindri into two areas, the northern area is known as "Tal". 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".
The total length of the Mahananda is 360 kilometres (220 mi), out of which 324 kilometres (201 mi) are in India and 36 kilometres (22 mi) are in Bangladesh.
The total drainage area of the Mahananda is 20,600 square kilometres (8,000 sq mi) out of which 11,530 square kilometres (4,450 sq mi) are in India.
The main tributaries of the Mahananda are Balason, Mechi, Kankai  and River Kalindri. At the East of the confluence of the Kalindri and the Mahananda lies the Old Malda town. In the Siliguri area it has three tributaries called the Trinai, Ranochondi and the pair of Chokor and Dauk taken as a single tributary.
The Kosi (Kausiki), which flows through the northeastern Bihar and joins the Ganges at a point much higher up than Rajmahal, originally ran eastward and fell into the Brahmaputra. The channel of the Kosi, therefore, must have been steadily shifting toward the west, right across the whole breadth of North Bengal. There was a time when the Kosi and the Mahananda joined the Karatoya and formed a sort of ethnic boundary between people living south of it and the Kochs and Kiratas living north of the river.
- Sharad K. Jain; Pushpendra K. Agarwal; Vijay P. Singh. Hydrology and Water Resources of India. p. 360. Google books. Retrieved 2010-05-14.
- "Rivers in Siliguri". Mahananda River. Siliguri on line. Retrieved 2010-05-14.
- "Rivers". Darjeeling News.Net. Retrieved 2010-05-14.
- "Mahananda Wildlife Sanctuary". nature beyond. Retrieved 2010-05-14.
- "News from Bangladesh". Retrieved 2010-05-14.
- "Uttar Dinajpur district". Uttar Dinajpur district administration. Retrieved 2010-05-14.
- "Kishanganj district". Kishanganj district administration. Archived from the original on 8 April 2010. Retrieved 14 May 2010.
- "Malda district". Malda district administration. Retrieved 2010-05-14.
- "Mahananda River". Britannica. Retrieved 2010-05-14.
- Majumdar, Dr. R.C., History of Ancient Bengal, first published 1971, reprint 2005, p. 4, Tulshi Prakashani, Kolkata, ISBN 81-89118-01-3.
- Sultana Nasrin Baby (2012), "Mahananda River", in Sirajul Islam; Ahmed A. Jamal, Banglapedia: National Encyclopedia of Bangladesh (Second ed.), Asiatic Society of Bangladesh
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