In Celtic folklore, the Irish: leannán sí (shee) "Barrow-Lover" (Scottish Gaelic: leannan sìth; Manx: lhiannan shee; is a beautiful woman of the Aos Sí (people of the barrow or the fairy folk) who takes a human lover. Lovers of the leannán sídhe are said to live brief, though highly inspired, lives. The name comes from the Gaelic words for a sweetheart, lover, or concubine and the term for a barrow or fairy-mound.

The leanan sídhe is generally depicted as a beautiful muse, who offers inspiration to an artist in exchange for their love and devotion; however, this frequently results in madness for the artist, as well as premature death.