Inocybe tahquamenonensis is a species of agaric fungus in the family Inocybaceae. Found in the United States, it was formally described in 1954 by mycologist Daniel E. Stuntz. The fruit bodies have bell-shaped to convex to flattened caps measuring 1.2–3 cm (0.5–1.2 in) in diameter. Its color is dark purplish brown to reddish- or blackish-brown, with reddish-purple flesh. The gills are attached to the stipe and are somewhat distantly spaced. They are initially reddish brown before tu