蝇蕈素（英语：muscimol、agarin、pantherine）是出现于大多数鹅膏菌属菇类的精神性生物碱，为γ-氨基丁酸A型受体的促效剂，并且会产生镇静安眠的效果。

蝇蕈素是造成毒蝇伞中毒反应的精神性化合物。当毒蝇伞在干燥的时候，鹅膏蕈氨酸，一种于毒蝇伞的神经性毒性次级代谢物，会作为前体药物，经由脱羧反应合成蝇蕈素。

Muscimol (also known as agarin or pantherine) is the principal psychoactive constituent of Amanita muscaria and related species of mushroom. Muscimol acts as a potent, selective agonist for the GABA_A receptors and displays sedative-hypnotic and dissociative psychoactivity.