Xenon Massive Detector for Dark Matter Searches (XMASS) is a multipurpose physics experiment in Japan. It is a large cryogenic storage dewar, a tank of liquid xenon equipped with photosensors monitoring flashes of light that might be caused by interactions with hypothetical dark matter particles. Unlike a cryogenic particle detector, it operates at temperatures relatively far from absolute zero. In addition to searching for dark matter, XMASS is also studying neutrinoless double beta decay and solar neutrinos. The project is conducted by a team at Institute for Cosmic Ray Research, University of Tokyo.