Mycenastrum is a fungal genus in the family Agaricaceae. The genus is monotypic, containing one widely distributed species, Mycenastrum corium, known by various common names: the giant pasture puffball, leathery puffball, or tough puffball.

The roughly spherical to turnip-shaped puffball-like fruit bodies grow to a diameter of 6–24 cm (2–9 in). Initially covered by a thick, felted, whitish layer, the puffballs develop a characteristic checkered skin (peridium) in age. As the spores mature, the gleba turns first yellowish then purplish brown. Spores are released when the peridium eventually splits open into irregularly shaped sections. Microscopically, the gleba consists of spherical, dark brown spores with rounded bumps on their surfaces, and capillitia—masses of intricately branched fibers—that form long thornlike spines.

The puffball grows on or in the ground in prairie or desert habitats. Although widely distributed, it is not commonly encountered. It is a threatened species in Europe. When the internal spore mass (the gleba) is firm and white, the puffball is edible, although some individuals may suffer mild gastrointestinal symptoms after eating it.

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