Ceratobasidium cornigerum is a species of fungus in the order Cantharellales. Basidiocarps (fruit bodies) are thin, spread on the substrate out like a film (effused) and web-like. A Rhizoctonia-like anamorphic state, sometimes referred to the genus Ceratorhiza, is frequently obtained when isolates are cultured. Ceratobasidium cornigerum is saprotrophic, but is also a facultative plant pathogen, causing a number of economically important crop diseases, and an orchid endomycorrhizal associate. The species is genetically diverse and is sometimes treated as a complex of closely related taxa.