''Arrhenia epichysium'' is a species of agaric fungus in the family Hygrophoraceae. It is found in Asia, Europe, and North America. The fruit body has small brown to dark gray caps measuring 1–3 cm in diameter. The cap color changes to light gray to tan when it is dry. Gills are narrow and thin, placed together closely, and decurrently attached to the stipe. The spores are smooth and ellipsoid, measuring 6–7.5 μm.