Moonchild (a.k.a., Liber LXXXI [Book 81], or The Butterfly Net) is a novel written by the British occultist Aleister Crowley in 1917.

Albeit not strictly a roman à clef, the novel depicts numerous acquaintances of Crowley's, thinly disguised fictional characters.

Arthur Edward Waite appears as a villain named Arthwaite, and the unseen head of the Inner Circle of which SRMD was a member.

Grey is attempting to save and improve the human race and condition by creating a homunculus, through impregnating the girl with the soul of an ethereal being—the Moonchild.

On 28 October 1929, the Aberdeen Press & Journal commented on Moonchild: We are constantly reminded of the moods of Anatole France and the methods of Rabelais.

[8] In Mark Frost's epistolary novel The Secret History of Twin Peaks, there is a chapter on Crowley which suggests that Moonchild was a source of inspiration for his and David Lynch's cult TV series Twin Peaks, particularly with its two warring lodges (a Black and a White Lodge), and several minor characters.

Prior to writing this novel, during a visit to New Orleans in December 1916, Crowley wrote a number of short stories where the character Simon Iff investigates various crimes and mysteries.