In Irish folklore, the female spirit who inspires poets and is considered a fairy mistress is the Leanan Sidhe.
The leannán sídhe is described as a beautiful woman of the Aos Sí, the fairy people associated with Ireland’s ancient mounds. She takes a human lover, often an artist or poet, and grants extraordinary inspiration in return for love and devotion.
The gift has a dark price. In the version popularized during the Celtic Revival, the inspired artist lives intensely but briefly, sometimes wasting away, going mad, or dying after becoming consumed by the supernatural relationship. This makes the Leanan Sidhe closer to a dangerous muse or fairy lover than to the harmless “muse” of ordinary usage.
Jane Wilde, writing as “Speranza,” mentioned the figure in her 1887 book Ancient Legends, Mystic Charms and Superstitions of Ireland. W. B. Yeats later popularized a more elaborate, almost vampiric interpretation. The name is often translated as “fairy lover” or “fairy mistress,” and spellings vary, including Leanhaun Shee and Leannan Sídhe.