The Lakhandei River is a river in southern Nepal

Nepal

Nepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...

 and in the state of Bihar

Bihar

Bihar is a state in eastern India. It is the 12th largest state in terms of geographical size at and 3rd largest by population. Almost 58% of Biharis are below the age of 25, which is the highest proportion in India....

 in India

India

India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

. It is a main tributary of the Bagmati River.

In Nepal, the river basin lies in the Sarlahi District

Sarlahi District

-Village Development Committees :*Achalgadh*Arnaha*Atrouli*Aurahi*Babarganj*Bagdaha*Bahadurpur*Balara*Bara Udhoran*Barahathawa*Basantapur*Batraul*Bela*Belhi*Belwajabdi*Bhadsar*Bhagawatipur*Bhaktipur*Bhawanipur*Brahmapuri*Chandra Nagar...

, and the river originates in the Sivalik Hills. The river enters India in the Sitamarhi district

Sitamarhi District

Sitamarhi is one of the districts of Bihar state, India, and Sitamarhi town is the administrative headquarters of this district. Sitamarhi district is a part of Tirhut Division.- History :...

 of Bihar

Bihar

Bihar is a state in eastern India. It is the 12th largest state in terms of geographical size at and 3rd largest by population. Almost 58% of Biharis are below the age of 25, which is the highest proportion in India....

, and flows through the town of Sitamarhi

Sitamarhi

Sitamarhi is a town and the district headquarters of Sitamarhi district, Bihar, India.-History:The name Sitamarhi, derives from "Sitamahi", meaning "hermitage of Sita". It is the mythological birthplace of Sita, and the spiritual centre of many sages and saints.This district is often bereaved by...

. It then enters the Muzaffarpur district

Muzaffarpur District

Muzaffarpur District is one of the thirty-eight districts of Bihar state, India, and Muzaffarpur town is the administrative headquarters of this district. Muzaffarpur district is a part of Tirhut Division....

, and joins the Bagmati at Katra (within the Muzaffarpur district).

The Lankhandei is known for flooding.