Armillaria umbrinobrunnea is a species of mushroom in the Physalacriaceae family. This species is found in South America. The beige to light brown caps of the mushroom are between 15 and 50 mm (0.6 and 2.0 in) in diameter, and densely covered in small scales. The species was originally collected in 1952 by Rolf Singer in Argentina, and named as the variety Armillariella montagnei var. umbrinobrunnea.