Mycena nargan, commonly known as the Nargan's bonnet, is a species of fungus in the Mycenaceae family, and the sole member of the section Nargan in the genus Mycena. Reported as a new species in 1995, it is known predominantly from Southern Australia. The saprobic fungus produces mushrooms that grow on well-decayed wood, often on the underside of wood lying in litter. The dark chestnut-coloured caps are covered with white, easily removed scales, and reach diameters of up to 2 cm (0.8 in) wide. The pale, slender stems are up to 5 cm (2.0 in) long and have white scales at the base. On the underside of the cap, the cream-coloured gills are widely spaced and bluntly attached to the stem. The edibility of the mushroom is unknown.