Non-native plants have been introduced to South Georgia since the first sealers inhabited the island in the late eighteenth century. The number of species and their impacts have varied over the years and today 41 non-native plant species are established and many threaten the native species and habitats of South Georgia. This is the first field guide to comprehensively treat these species, providing full colour photographs, distribution maps and species descriptions, plus keys to the grasses and sedges. This guide is accessible to all and also provides an opportunity for visitors to be part of a citizen science programme contributing sightings and improving our knowledge of the introduced flora of South Georgia.