The 3rd Iberian Space Science Summer School (i4s) will provide high-level professional training for early-career researchers, scientists, and entrepreneurs in the domain of Space Weather, with an emphasis on the fundamental science of the Sun-Earth system, including modelling and forecasting, and its impact on society. The School is also an opportunity to foster the scientific collaboration between researchers, to promote and encourage the vocations of young researchers, and to help disseminate research in Space Science.