Conditions in arctic and alpine ecosystems impose great challenges to the plants and other organisms that live there. Despite this, thousands of plant species worldwide survive or even prosper under the extreme climatic, edaphic, and ecological conditions in the High North (or South) and in the high mountains. Despite the long tradition of alpine and arctic research, there is still much to be discovered. Arctic and alpine plants continue to surprise researchers with their ingenious strategies and adaptations. Today, global warming, the ever-increasing demand for resources, and the development of tourism are growing threats to arctic and alpine plant life, even in the most remote regions of the world. The future of these highly specialized organisms is uncertain. This applies not only to glacial relics and endemics in isolated mountain refugia, but also to tundra areas that were intact until recently and are now under increasing pressure from man-made global changes. This Special Issue presents reviews and research articles that explore historical biogeography, ecology, adaptations, impacts of global change, and conservation issues related to alpine and arctic plants using a variety of ecological, biogeographical, evolutionary, physiological, and genetic approaches.