Lake Eiði (Faroese: Eiðisvatn) is a lake on the island of Eysturoy in the Faroe Islands.

[1] It is the fifth-largest natural lake in the Faroe Islands, with a natural size of 47 hectares (120 acres) that has been increased to 1.14 square kilometers (0.44 sq mi).

[2] The size of the lake was increased by walls 22 and 13 m high, constructed by the SEV company in connection with the Eiði power plant, which uses the lake as a reservoir.

Electricity production was started in 1987.

[3] Two tunnels redirect water from adjacent valleys to Eiði.