Safeguarding Mountain Ecosystems: A Global Challenge provides an overview of the relevant research in mountain regions worldwide, identifying existing challenges and providing an understanding of the diversity of mountain ecosystems in different regions. Mountain ecosystems are increasingly vulnerable to modified climate conditions and other global changes (demographic, migration, urbanization). In this time of change, efforts for sustainable development in mountain ecosystems deserve all the attention, especially in synergy with the United Nations’ International Frameworks, including the Sustainable Development Agenda 2030, the Sendai Framework for Disaster Risk Reduction, the Paris Agreement, and the New Urban Agenda.Sections underline the importance of mountain regions for humanity at global, regional and local scales, describe the challenges of safeguarding mountains and possible solutions worldwide, and scrutinize regional specificities of the major mountain ranges, describing the challenges and opportunities of each. Final sections reflect on applications and technologies that address and solve major problems.