Caldicellulosiruptor saccharolyticus is a species of thermophilic, anaerobic cellulolytic bacteria. It was isolated from a piece of wood floating in the flow from a freshwater thermal spring in New Zealand in 1987, and tentatively named Caldocellum saccharolyticum. In 1994, the isolate was more thoroughly characterized physiologically, and classified to a new genus, Caldicellusiruptor, based on 16S RNA sequence. It is the type species, and more thoroughly studied member of its genus.