Ganoderma megaloma

''Ganoderma megaloma'' is a species of bracket fungus in the family Ganodermataceae. Described as new to science in 1846 by mycologist Joseph-Henri Léveillé, it is found in the eastern and midwestern United States. It was moved into the genus Ganoderma by Giacomo Bresàdola in 1912. The fungus causes white rot and butt rot on living hardwoodss. The holotype was collected in New York.

It is closely related to Ganoderma applanatum, however DNA analysis reveals that G. applanatum is a European species which does not occur in the US.