|Max. length||836 metres (2,743 ft)|
|Max. width||427 metres (1,401 ft)|
|Surface area||24.47 hectares (60.5 acres)|
|Average depth||4.58 metres (15.0 ft) (average)|
|Max. depth||15 metres (49 ft)|
|Surface elevation||3,753 metres (12,313 ft)|
Tsomgo Lake, also known as Tsongmo Lake or Changgu Lake, is a glacial lake in the East Sikkim district of the Indian state of Sikkim, some 40 kilometres (25 mi) from the capital Gangtok. Located at an elevation of 3,753 m (12,313 ft), the lake remains frozen during the winter season. The lake surface reflects different colours with change of seasons and is held in great reverence by the local Sikkimese people. Buddhist monks prognosticated after studying the changing colours of the lake.
The lake is surrounded by steep mountains which are covered with snow during winter. During summer the snow cover melts and forms the source for the lake. The lake which remains frozen in winter season, sometimes extending up to May, receives an average annual precipitation of 1,183 millimetres (46.6 in) with temperatures recorded in the range of 0–25 °C (32–77 °F). 
The lake is about 40 kilometres (25 mi) away from Gangtok on the Gangtok-Nathula highway. Further, the road to Nathu La skirts the lake on the north side. The Chinese border crossing is only some 5 kilometres (3.1 mi) east-northeast in a straight line, but some 18 kilometres (11 mi) by road.
The lake is formed in an oval shape and has a surface area of 24.47 hectares (60.5 acres). The maximum length of the lake is 836 metres (2,743 ft) and has a maximum width of 427 metres (1,401 ft). The maximum depth reported is 15 metres (49 ft) while the average depth is 4.58 metres (15.0 ft). The lake water quality is of moderate turbidity.
The lake is the venue for the Guru Purnima festival which is also the Raksha Bandhan festival when the faith healers known as Jhakris of Sikkim assemble at the lake area to derive benefits from the healing qualities of the lake waters.
Alpine forests cover the catchment of the lake. After the winter season ends in middle of May, the periphery of lake has scenic blooms of flower species of rhododendrons (the state tree of Sikkim), primulas, blue and yellow poppies, irises and so forth. Also seen in the precincts of the lake are several species of birds including Brahminy ducks. Wildlife seen includes the red panda.
As the lake is located in a restricted area it is essential for all Indians visiting the area to obtain permits. In case of foreign nationals special permit is essential.
Border trade market
|Wikimedia Commons has media related to Tsomgo Lake.|
- "Tsomgo (Changu) Lake". Sikkim Tourism:Government of Sikkim.
- "Tsomgo Lake". National Informatics Centre.
- Kar 2014, p. 101.
- deBruyn, Pippa; Bain, Keith; Venkatram, Niloufer; Joshi, Shonar (4 March 2008). Frommer's India (Frommer's Complete). Hoboken, New Jersey, USA: Frommer's. p. 586. ISBN 978-0-470-16908-7. Retrieved 29 November 2009.
- O'Neill, A. R. (2019). "Evaluating high-altitude Ramsar wetlands in the Sikkim Eastern Himalayas". Global Ecology and Conservation. 20 (e00715): 19. doi:10.1016/j.gecco.2019.e00715.
- "Changu Lake stamp and Sikkim Philately". Sikkimphilatelic Society.
- "Documents signed between India and China during Prime Minister Vajpayee's visit to China". Ministry of External Affairs, Government of India. 23 June 2003. Retrieved 27 March 2021.