Mairu (plural: mairuak), also called Maideak, Mairiak, Saindi Maidi (in Lower Navarre), Intxisu in the Bidasoa valley are creatures of Basque mythology. They were giants who built dolmens or harrespil. Like the dolmens, they are only found in mountains. They are often associated with lamia, though these are known in all the Basque Country.
In parts of Spain, any ancient monument was popularly attributed to the age of Moorish domination. The origin of the Mairu is thought to be as old as the "mouros encantados" in Portuguese (Spanish: moros encantados), who are thought to be the remnant of old pre-Roman deities.
See also 
- Anuntxi Arana: Mari, mairu eta beste - 1996 - Bulletin du musée basque n°146.
- Mairu in the Online Morris Basque-English dictionary.