The chytridiomycotes (chytrids) are zoosporic fungi having simple thalli. Most species inhabit in freshwater but marine and terrestrial species are also known. They are saprobic or parasitic. The Chytridiomycota includes Batrachochytrium dendrobatidis (Chytridiomycetes) causing a famous infectious disease of amphibians, chytridiomycosis.

The thallus of the Chytridiomycota is monocentric, polycentric or filamentous. The flagellate cell possesses a centriole, nine flagellar props and a microbody-lipid globule complex. Nuclear envelope is fenestrated at poles during mitosis. Asexual reproduction by uniflagellate zoospores. Species with sexual reproduction show zygotic meiosis.

All zoosporic species of the Fungi (true fungi) were traditionally classified into the Chytridiomycota. However, some 'chytrids' sensu lato have been transferred to new phyla (e.g. Blastocladiomycota) because they are distantly related phylogenetically.