In the late eighteenth century, the first sealing ships from England arrived in South Georgia. With them came a host of invasive plants, which set to work upending the island ecosystem. Today, forty-one non-native plant species are established in the region and, even a century later, they continue to threaten the native species and habitats of South Georgia. This is the first field guide to comprehensively cover these species, providing full-color photographs, distribution maps, and species descriptions, plus keys to the grasses and sedges of the area. This guide is accessible even to non-botanists and also provides an opportunity for visitors to be part of a citizen science program contributing sightings and improving our knowledge of the introduced flora of South Georgia.