Tree canopies are one of the most recognizable features of forests, providing shelter from external influences to a myriad of species that live in the understorey. Canopy disturbances are now accelerating across European forests, and climate-change induced drought is a key driver. These disturbances are opening the canopy and exposing forest biodiversity to no-analog light regimes and drought – light and drought levels they have never been exposed to before. As the majority of forest plant species occur in the shade below tree canopies, the combination of altered light regimes and intensifying droughts can strongly impact forest biodiversity. However, the interactive effects of novel light regimes and drought on temperate forest biodiversity have never been investigated before. Since recent European droughts are unprecedented in the last two millennia, and this has initiated the largest pulse of forest disturbances in almost two centuries, the time to assess impacts on biodiversity is now. The overarching aim of CanopyChange is to quantify, understand and predict the impacts of no-analog light regimes and drought on below-canopy forest plant biodiversity. To address this challenging goal, cross-continental resurveyed vegetation plots, the first pan-European forest disturbance-drought experiment, and a pioneering canopy clipping mesocosm experiment will be combined with an interdisciplinary toolbox drawing from ecology, forestry, and climatology. These data will then feed into cutting-edge joint species distribution models to project European forest plant biodiversity responses to future climate and canopy change. CanopyChange will be the first integrative study of pan-European forest plant biodiversity responses to no-analog light regimes and drought. CanopyChange is at the heart of biodiversity conservation and forest management, and will deliver much-needed information for policy makers and managers to adapt to the future, no-analog conditions in European forests.