(Fr.) Fr. (1863)
(Fr.) Quél. (1888)
Inocybe is a large genus of mushroom-forming fungi with over 1400 species, including all forms and variations. Members of Inocybe are mycorrhizal, and some evidence shows that the high degree of speciation in the genus is due to adaptation to different trees and perhaps even local environments.
The name Inocybe means "fibrous hat". It is taken from the Greek words ἴς (in the genitive ἴνος, meaning “muscle, nerve, fiber, strength, vigor”) and κύβη (“head”).
The genus was first described as Agaricus trib. Inocybe by Swedish scholar Elias Magnus Fries in volume 1 of his work, Systema mycologicum (1821), and verified in the volume 2 of his book Monographia Hymenomycetum Sueciae in 1863. All other renaming attempts are accepted synonymous 
Typical mushrooms of the genus have various shades of brown, although some lilac or purplish species exist. Caps are small and conical, though flattening somewhat in age, generally with a pronounced central umbo. The cap often appears fibrous, giving the genus its common name of "fiber caps". Many species have a distinctive odor, various described as musty or spermatic.
Description valid for most species:
Originally placed in the family Cortinariaceae (later shown to be polyphyletic), phylogenetic analyses suggests that the genus is better placed as the type genus of the family Inocybaceae.
Inocybe species are not considered suitable for consumption, although in some underdeveloped countries certain species of Inocybe mushrooms are eaten. Many species contain large doses of muscarine, and no easy method of distinguishing them from potentially edible species exists. In fact, Inocybe is the most commonly encountered mushroom genus for which microscopic characteristics are the only means of certain identification to the species level. While the vast majority of Inocybes are toxic, seven rare species of Inocybe are hallucinogenic, having been found to contain psilocybin, including Inocybe aeruginascens which also contains aeruginascine (N, N, N-trimethyl-4-phosphoryloxytryptamine).
Two supersections are informally recognized: Cortinate supersection: The stipe is only pruinose at the apex or the upper half. The stipe base is (generally) not bulbous and a remnant of a cortina is present in the margin of the young cap. Marginate supersection: The stipe are entirely pruinose and has a bulbose base as general.
Also, several subgenera/sections are recognized:
This subgenus has pleurocystidia, usually thick-walled and in the apex has crystals. The basidiospores are smooth or angular-nodulose. The basidia is not necropigmented (basidia that become ochraceous and collapse). The hilar appendice is conspicuous. This subgenera is cosmopolitan and frequent in temperate ecosystems.
This subgenus has no pleurocystidia and has necropigmented basidia. The spores are smooth and the hilar appendix is inconspicuous. Large cheilocystidia (>50 um). This is known from tropical Africa, Tropical, India and temperate Australia.
Inosperma (now a separate genus)
The fruiting bodies of this subgenus usually have a distinct odor (fruity, honey-like, fishy). The pileus is radially rimose ("Rimosae") or can be squamulose to squarrose ("Cervicolores"). The lamella has no pleurocystidia, but has cheilocystidia. Basidia necropigmented or not. The spores are smooth. In temperate areas. Wide distribution.
The cap is usually woolly-squamulose, the cap surface is conspicuously darkening with alkali. The lamella broadly adnate to subdecurrent. The stipe is shorter and has not pleurocystidia. The basidia are necropigmented and there are also cheilocystidia as terminal elements. Spores smooth. Wide distribution
The lamellae have no pleurocystidia but there are cheilocystidia. Spores smooth. Known from tropical India.
Fruitbodies have indistinct, spermatic or green corn odor. The pileus is radially rimose or rimulose, never squarrulose and rarely squamulose. Pleurocystidia are absent and cheilocystida are present. Spores smooth. Wide distribution.
Small fruiting bodies with tubarioid or omphalinoid habit. Decurrent lamellae and cheilocystiidia present. Spores smooth. Known from mediterranean and tropical Africa.
The genus Inocybe is very species-rich. The genus is divided according to Bon (2005) into three subgenera with sections:
Main article: List of Inocybe species
There are hundreds of species of Inocybe. Representatives of the genus include: