| Lachen River | |
| Subdivision Type1: | Country |
| Subdivision Name1: | India |
| Source1: | Himalayas |
| Source1 Location: | Himalayas, Sikkim, India |
| Mouth: | Teesta River |
| Mouth Location: | Mangan district, Sikkim, India |
The Lachen River is a tributary of the Teesta River in the state of Sikkim, India. It is one of the two main tributaries of the Teesta along with the Lachung River, which rise on opposite sides of the Donga Range in neighbouring Bhutan[1] and converge in Chungthang in the North Sikkim district.[2]