Cystangium is a genus of fungi in the family Russulaceae.

The genus contains 32 species that are distributed in Australia and South America.

[1] Cystangium was described by American mycologists Rolf Singer and Alexander H. Smith in 1960.

[2] The taxon is phylogenetically part of Russula and thus probably a synonym.

[3] However, it has not been formally synonymised yet and continues to be used by taxonomists.