The lamiak is a siren- or nereid-like creature in Basque mythology. Lamiak live in the river. They are very beautiful, and stay at the shore combing their long hair with a golden comb; they easily charm men. They have duck feet.
Lamiak help those who give them presents by providing them with help at work; if a farmer left them food at the river shore, they would eat it at night and in exchange would finish a field he had left unploughed. In some places, bridges were believed to have been built at night by lamiak: Ebrain (Bidarray, Lower Navarre), Azalain (Andoain, Gipuzkoa), Urkulu (Leintz-Gatzaga, Gipuzkoa), Liginaga-Astüe (Labourd).
In some places lamiak had to go away if the bridge they were building at night was left unfinished at cockcrow. People believed that lamiak had left a river if a stone of the bridge was missing. Most lamiak disappeared when men built small churches in the forest.
A lamiak is at the other side of the rainbow combing her hair. When the sun lights her hair, the rainbow opens.
In some places male lamiak also exist; they are strong and have built dolmens at night. Sometimes they can enter a house when its inhabitants are sleeping. They are given different names: Maideak, Mairiak, Mairuak, Intxixuak (in Oiartzun, (Gipuzkoa), Saindi Maidi (in Lower Navarre).
Many toponyms are related to lamiak: Lamikiz (Markina), Laminaputzu (in Zeanuri), Lamitegi (in Bedaio), Lamirain (in Arano), Lamusin (in Sare), Lamiñosin (in Ataun).