Lake Monowai (officially Monowai Lake; Māori: Manokīwai) is a large lake (31 square kilometres or 12 square miles) in the southern part of Fiordland National Park, in New Zealand's South Island, 120 kilometres northwest of Invercargill.

[1] At an altitude of 196 metres in a long curved valley, the lake appears on maps shaped like a letter "U".

The western part of the lake is set in beautiful mountainous country.

One of the South Island's oldest hydroelectric stations is powered by the waters of the Monowai.

[2] As a result of the Save Manapouri campaign, plans to raise the level of the lake to create more hydroelectric power were shelved by the Labour government of Norman Kirk in the 1970s, and an independent body, the Guardians of Lake Manapouri, Monowai, and Te Anau was created to oversee management of the lake levels (more information at Manapouri Power Station).