AbstractThe conversion of charge current into spin current by the Rashba–Edelstein effect enables the reciprocal control of electron charge and magnetization in magnetoelectric and magneto‐optical devices. The fundamentals of this effect are described in 3D lead‐halide perovskites: due to spin‐momentum locking, a strong charge‐spin conversion, widely tunable by the injected charge density, is envisaged. The analysis highlights the close relationship between charge‐spin conversion and the topological transition occurring from the low‐density, torus‐shaped Fermi surface (genus 1) to the high‐density, simply connected Fermi surfaces (genus 0). At room temperature, spin‐polarizations as large as ≈10% are obtained for input charge currents in the ≈102 to 106 Acm−2 range; at low temperature, almost full spin‐polarization can be achieved, owed to the large, impurity scattering‐limited mobilities. The results qualify lead‐halide perovskites as suitable materials for spin‐orbitronic applications.