The gasteroid fungi are a group of fungi in the Basidiomycota. Species were formerly placed in the obsolete class Gasteromycetes Fr. (literally "stomach fungi"), or the equally obsolete order Gasteromycetales Rea, because they produce their spores inside their basidiocarps (fruit bodies) rather than on an outer surface. The class is artificial, however, since species—which include puffballs, earthstars, stinkhorns, and false truffles—are not closely related to each other. Because they are often studied as a group, it has been convenient to retain the informal (non-taxonomic) name of "gasteroid fungi".
Several gasteroid fungi—such as the stinkhorn, Phallus impudicus L.—were formally described by Linnaeus in his original Species Plantarum of 1753, but the first critical treatment of the group was by Christiaan Hendrik Persoon in his Synopsis methodica fungorum of 1801. Until 1981, this book was the starting point for the naming of Gasteromycetes under the International Code of Nomenclature for algae, fungi, and plants. Although the starting point was subsequently put back to 1753, names of gasteroid fungi used in Persoon's book are still sanctioned and cannot be replaced by earlier names.Elias Magnus Fries introduced the name Gasteromycetes for a class of fungi in his Systema Mycologicum of 1821, although (not using a microscope) he included many species of the Ascomycota (such as truffles) within the class. Fries contrasted the Gasteromycetes with the Hymenomycetes, where spores are produced externally on gills, pores, and other surfaces.