Lake Naivasha is a freshwater lake in Kenya, outside the town of Naivasha in Nakuru County, which lies north west of Nairobi. It is part of the Great Rift Valley. The name derives from the local Maasai name Nai'posha, meaning "rough water" because of the sudden storms which can arise.
is at the highest elevation of the Kenyan Rift valley at 1,884 metres (6,181 ft) in a complex geological combination of volcanic rocks and sedimentary deposits from a larger Pleistocene era lake.
Apart from transient streams, the lake is fed by the perennial Malewa and Gilgil rivers. There is no visible outlet, but since the lake water is relatively fresh it is assumed to have an underground outflow.
The lake has a surface area of 139 km²,  and is surrounded by a swamp which covers an area of 64 square km, but this can vary largely depending on rainfall. It is situated at an altitude of 1,884 metres (6,180 ft). The lake has an average depth of 6 m (20 ft), with the deepest area being at Crescent Island, at a maximum depth of 30 m (100 ft). Njorowa Gorge used to form the lake's outlet, but it is now high above the lake and forms the entrance to Hell's Gate National Park. The town of Naivasha (formerly East Nakuru) lies on the north-east edge of the lake.
Between 1937 and 1950, the lake was used as a landing place for flying boats on the Imperial Airways passenger and mail route from Southampton in Britain to South Africa. It linked Kisumu and Nairobi. Joy Adamson, the author of Born Free, lived on the shores of the lake in the mid-1960s. On the shores of the lake is Oserian ("Djinn Palace"), which gained notoriety in the Happy Valley days between the two world wars. It now forms part of the Oserian flower farm. In 1999, the Lake Naivasha Riparian Association received the Ramsar Wetland Conservation Award for its conservation efforts regarding the Lake Naivasha Ramsar site.