Harmaja (Swedish: Gråhara) is an island and a lighthouse outside Helsinki, south of the Suomenlinna sea fortress.

A landmark structure was built on the island in the 18th century and a light house in 1883.

In 1900 the height was doubled by creating a rectangular brick building on a granite base.

A large foghorn alerted ships in fog and in bad visibility.

Harmaja received the world's first directed and undirected radio beacon in 1936.