PHUSICOS, meaning 'According to nature' in Greek, demonstrates how nature-based solutions (NBSs) provide robust, sustainable and cost-effective measures for reducing the risk of extreme weather events in rural mountain landscapes. Although mountains amplify risks, and even more so under extreme weather events, mountainous regions do not receive the same attention as densely populated urban areas in European disaster risk reduction plans. PHUSICOS's underlying premise is that nature itself is a source of ideas and solutions for mitigating the risk posed by climate-driven natural hazards. However, there is a lack of adequate proof of concept for NBSs to address hydro-meteorological events in rural and mountainous regions. PHUSICOS will fill the knowledge gap specifically related to NBSs for hydro-meteorological hazards (flooding, erosion, landslides and drought) by implementing NBSs at several European case study sites. These sites comprise 3 large-scale demonstrator sites Italy, Frane/Spain/Andorra and Norway; and 2 small-scale complementary concept cases in Austria and Germany. The three demonstrator sites are representative of hydro-meteorological hazards, vegetation, topography and infrastructure throughout rural and mountainous regions in Europe. They have already guaranteed external financing and are currently in the process of implementing disaster risk reduction measures that are open to broader implementation of NBSs through the application of the PHUSICOS key innovation actions. The concept cases will be used for testing innovative ideas at local scale. PHUSICOS relies on a transdisciplinary consortium of 15 partners from seven European Countries, with expertise from public authorities, research institutes and universities to develop innovative actions on five fronts: technical, service, governance, learning arena and product innovations. PHUSICOS will also utilise the experience of three international partners and results of European research projects.