During the geological history of the Earth, evolutionary competition for dissolved silicon in the ocean directly influenced changes in the global cycles of silicon, carbon, and other nutrients that regulate ocean productivity and ultimately the Earth’s climate. Radiolarians are key players of this evolution and, as such, have provided rich palaeontological records for a multitude of palaeoceanographic studies. These marine micro-organisms, which can produce intricate skeletons of silica, are very sensitive to changes in environmental conditions. The resistant silica-based skeletons of radiolarians are particularly useful in regions of importance for studying climate change where carbonate-based archives are poorly preserved (e.g. Southern Ocean) and offer a biogeochemical window into the mid-depth section (i.e. 30-500 m) of the marine environment. The mid-depth zone in the marine environment is currently inaccessible for Si cycle palaeo-reconstructions and its characterization is pivotal to the detection of glacial–interglacial changes in water column stratification, which plays a critical role during periods of abrupt climate change. Fortunately, radiolarians are common plankton found in this mid-depth zone. However, in contrast to other silicifying organisms found in the palaeo-record, such as deep-water sponges and surface dwelling diatoms (unicellular silicifying micro-algae), the use of radiolarian geochemistry to describe palaeoceanographic variation in dissolved Si (DSi) is very much in its infancy largely due to the challenges associated with their growth under laboratory-controlled conditions and limited knowledge on the factors that govern their contemporary biogeographic distribution. The RadiCal project offers to develop Radiolarians as a novel palaeo-proxy for marine silicon cycling by Calibrating the silicon stable isotope composition (d30Si) of these organisms to their modern environment. This objective will be achieved by applying an innovative multidisciplinary approach evaluating the influence of the modern environment and taxonomy on the variability of radiolarian silicon isotope fractionation (1) in situ, (2) under laboratory-controlled conditions, and (3) from a core-top calibration study from a variety of different oceanographic basins within the Southern Ocean. RadiCal fosters the innovative and inter-disciplinary approach of the P.I., which aims to combine non-traditional stable isotope biogeochemistry with in situ observations, in vitro experimental culture experiments, and sediment core samples in order to answer questions regarding the role of marine silicifiers (e.g. radiolarians) on the global cycling of Si. The RadiCal project will also develop collaborations between French and foreign scientists, strengthen the link between internationally recognized laboratories, and aggregate a community of researchers with diverse expertise on silicifying organisms (e.g. radiolarians) while developing potential for further collaboration and development of larger scale projects (e.g. ERC). In addition, the project RadiCal will permit the training of a new generation of oceanographers using an innovative and multi-disciplinary approach.