Early actinide ions have large spin‐orbit couplings and crystal field interactions, leading to large anisotropies. The success in using actinides as single‐molecule magnets has so far been modest, underlining the need for rational strategies. Indeed, the electronic structure of actinide single‐molecule magnets and its relation to their magnetic properties remains largely unexplored. A uranium(III) single‐molecule magnet, [U^III{SiMe₂NPh}₃‐tacn)(OPPh₃)] (tacn=1,4,7‐triazacyclononane), has been investigated by means of a combination of magnetic, spectroscopic and theoretical methods to elucidate the origin of its static and dynamic magnetic properties.