Cordyceps /ˈkɔːrdɪsɛps/ is a genus of ascomycete fungi (sac fungi) that includes over 260 species worldwide, many of which are parasitic. Diverse variants of cordyceps have had more than 1,500 years of use in Chinese medicine. Most Cordyceps species are endoparasitoids, parasitic mainly on insects and other arthropods (they are thus entomopathogenic fungi); a few are parasitic on other fungi.

The generic name Cordyceps is derived from the ancient Greek κορδύλη kordýlē, meaning "club", and the Latin -ceps, derived from Latin caput, meaning "head". The genus has a worldwide distribution, with most of the known species being from Asia.

There are two recognized subgenera:

Cordyceps sensu stricto are the teleomorphs of several genera of anamorphic, entomopathogenic fungi such as Beauveria (Cordyceps bassiana), Septofusidium, and Lecanicillium.

Cordyceps subgen. Epichloe was at one time a subgenus, but is now regarded as a separate genus, Epichloë.

Cordyceps subgen. Ophiocordyceps was at one time a subgenus defined by morphology. Nuclear DNA sampling done in 2007 shows that members, including "C. sinensis" and "C. unilateralis", as well as some others not placed in the subgenus, were distantly related to most of the remainder of species then placed in Cordyceps (e.g. the type species C. militaris). As a result, it became its own genus, absorbing new members.

The 2007 study also peeled off Metacordyceps (anamorph Metarhizium, Pochonia) and Elaphocordyceps. A number of species remain unclearly assigned and provisionally retained in Cordyceps sensu lato.

There are over 260 species in the genus Cordyceps including the following species: