Mosses are a major component of the vegetation in ice-free coastal regions of Antarctica. They play an important role in the colonisation of ice-free terrain, accumulation of organic matter, release of organic exudates, and also provide a food and habitat resource for invertebrates. They serve as model organisms for physiological experiments designed to elucidate problems of plant cold tolerance and survival mechanisms and for monitoring biological responses to climate change. This Flora provides the first comprehensive description, with keys, of all known species and varieties of moss in the Antarctic biome. It has involved microscopic examination of around 10,000 specimens from Antarctica and, for comparison, from other continents. All species are illustrated by detailed line drawings, alongside information about their reproductive status, ecology, and distribution. This is an invaluable resource for bryologists worldwide, as well as to Antarctic botanists and other terrestrial biologists.