This data release contains the stable silicon isotope composition of living siliceous Rhizaria collected from the Mediterranean Sea (MS) and the Southern Ocean (SO), and co-located seawater silicon isotopic compositions. It also contains the stable silicon isotope composition of core-top samples from the southern Atlantic, Indian, and Pacific Oceans as well as the Southern Ocean. Three taxonomic Orders of siliceous Rhizaria (namely Spumellaria, Nassellaria, and Phaeodaria) were measured for their 𝛿30Si, and, whenever possible, provide species-specific information.The samples were collected as part of the RadiCal project funded by the French National Research Agency (18-CEO1-0011-01).