2C-B-ButterFLY, also known as 2C-B-BFLY or as 2C-B-MOTH, is a serotonin receptor modulator of the phenethylamine, 2C, and FLY families. It is a conformationally-restricted derivative of the psychedelic drug 2C-B and a ring-expanded homologue of the better-known compound 2C-B-FLY.