Lake Manapouri is a lake in the South Island of New Zealand.

Lake Manapouri has four arms: North, South, West and Hope - and some 33 islands, 22 of which are wooded. The Waiau River forms the lake's natural outlet.

The lake provides hydro-electric power via the Manapouri Power Station sited in the lake's West arm. The station discharges water 10km away through a tailrace tunnel to Doubtful Sound and the sea. In 1960, it was proposed to raise the lake by up to 30 metres for the power station but a strong nationwide protest during the 1960's prevented this from happening. The lake levels are instead carefully controlled to be close to natural fluctuations.

The lake is within the boundary of the Fiordland National Park and the Te Wahipounamu World Heritage site.