A preferred embodiment of the invention relates to a cyclone separator for a vacuum toilet system, with a casing; an input-side swirl generator, whose input openings impart a swirl to the inflowing fluid; a separating wall arranged in the casing, which encloses the fluid stream in the cyclone separator ring-like and whose interior cross section tapers downstream; and a collection tank in the casing for receiving and accumulating constituents separated out of the fluid. In addition, the invention relates to a wastewater tank and vacuum toilet system having such a cyclone separator.