Panaeolus cinctulus is a species of mushroom in the family Bolbitiaceae. It is commonly known as the banded mottlegill or weed panaeolus. This mushroom is noted for its psychoactive properties due to the presence of psilocybin, though its potency is generally lower compared to other psilocybin-containing species.

Panaeolus cinctulus is widely distributed and can be found in various habitats, including lawns, compost, gardens, and dung. It is a saprotrophic species, meaning it feeds on decaying organic matter, and typically appears from spring to autumn.

Morphologically, Panaeolus cinctulus has a brown to reddish-brown cap that can be conical or bell-shaped, sometimes flattening with age. The cap often features a darker band around the margin, which gives the species its “banded” nickname. The gills are dark and mottled, a characteristic feature of the Panaeolus genus. The stem is slender, often pale to dark brown, and lacks a ring.

Due to its widespread occurrence and psychoactive properties, Panaeolus cinctulus is of interest to both mycologists and those studying the effects of psilocybin. However, it should be approached with caution, as accurate identification is essential to avoid confusion with non-psychoactive or toxic species.

This species is sometimes confused with other psychoactive Panaeolus species, though reports of its psychoactivity are limited and inconsistent. Gymnopilus aeruginosus is more often studied for its ecological role in wood decomposition rather than its psychoactive properties. As with all wild mushrooms, proper identification is crucial, as some species in the Gymnopilus genus can be toxic.