Tradition: Irish Mythology
Alternative Names: Aos Sídhe, Daoine Sí, Daoine Uaisle, Daoine Maithe, Sídhfir, Fair Folk
Category: Fairy
The Myth
The Aos Sí are a supernatural people of Irish folklore, traditionally associated with the mysterious mounds and hills known as sí or sídhe. They are often described as extraordinarily beautiful beings, although they can also appear terrible or hideous. Their nature varies across tradition: they may be understood as descendants of the Tuatha Dé Danann, spirits of nature, divine beings, ancestors, or, in another tradition, fallen angels whose sins were not great enough to send them to Hell. In stories connecting them to the Tuatha Dé Danann, they withdrew into the Otherworld after the arrival of the Milesians and came to dwell beneath the earth in their hidden halls and fairy mounds.
The Aos Sí inhabit fairy hills, ancient mounds, fairy rings, sacred trees such as whitethorns, lakes, and forests. These places are their homes and are fiercely protected, and people who disturb them may suffer supernatural retaliation. They can drive intruders away, kidnap humans, or take children and replace them with changelings. Their presence is especially associated with liminal moments such as dusk and dawn, when the Otherworld is believed to come closest to the human world, as well as festivals such as Samhain, Bealtaine, and Midsummer. People therefore traditionally avoided offending them and left offerings to win their goodwill, often referring to them indirectly as the “Good Neighbours,” the “Fair Folk,” or simply “the Folk.”
The Aos Sí encompass many different supernatural beings and manifestations. The bean sídhe, or banshee, is a woman of the fairy mound whose wailing announces an approaching death, while other related beings include the fairy lover leanan sídhe, the fairy cat cat-sìth, the fairy dog cù-sìth, and the supernatural hosts known as the sluagh sídhe. The sídhe themselves are the mounds, halls, courts, or residences of these beings rather than the name of the people who inhabit them. Across Irish folklore, the Aos Sí therefore form a vast supernatural community inhabiting a hidden Otherworld that exists alongside the human world, capable of granting blessings and gifts but also bringing illness, misfortune, madness, or death when their boundaries are violated.
Sources
“Aos Sí.” Wikipedia: The Free Encyclopedia. Wikimedia Foundation. Accessed October 5, 2026. https://en.wikipedia.org/wiki/Aos_S%C3%AD