Chytridiomycetes is a class of fungi. Members are found in soil, fresh water, and saline estuaries. They are primitive fungi, and are first known from the Rhynie chert. It has recently been redefined to exclude the taxa Neocallimastigomycota and Monoblepharidomycetes, which are now a phylum and a sister-class respectively. It includes the genera Olpidiopsis and Hypochytrium in addition to the type genus.