To understand the processes involved in the deep interior of the Earth and explaining its evolution, in particular the dynamics of the Earth’s fluid iron-rich outer core, only indirect satellite and ground observations are available. They each provide invaluable information about the core flow but are incomplete on their own: - The time dependent magnetic field, originating mainly within the core, can be used to infer the motions of the fluid at the top of the core on decadal and subdecadal time scales. - The time dependent gravity field variations that reflect changes in the mass distribution within the Earth and at its surface occur on a broad range of time scales. Decadal and interannual variations include the signature of the flow inside the core, though they are largely dominated by surface contributions related to the global water cycle and climate-driven land ice loss. - Earth rotation changes (or variations in the length of the day) also occur on these timescales, and are largely related to the core fluid motions through exchange of angular momentum between the core and the mantle. The GRACEFUL project will go beyond the potential of individual satellite and ground observations and will combine the information about the core deduced from the gravity field, from the magnetic field and from the Earth rotation in synergy, in order to examine in unprecedented depth the dynamical processes occurring inside the core and at the core-mantle boundary. We will develop cutting-edge algorithms to process observational data and use up-to-date numerical models of the core flow to infer its dynamics. This interdisciplinary approach will challenge our current understanding of the core dynamics and provide a step change in our understanding of the deep Earth’s interior. The pioneering approach of GRACEFUL will provide an innovative template to obtain totally novel information about the dynamic processes inside the fluid core and core-mantle boundary of the Earth.