The distribution of electrons in the 4f orbitals of lanthanide ions is often assigned a crucial role in the design of single-molecule magnets (SMMs), which maintain a magnetization in zero external field. Optimal spatial complementarity between the 4f-electron density (4f-ED) and the ligand field is key to maximizing magnetic anisotropy-an important factor in the ability of lanthanide complexes to display SMM behaviour. Here, we have experimentally determined the ED distribution in two dysprosium molecular complexes by interpreting high-resolution synchrotron X-ray diffraction with a multipole model. The ground-state 4f-ED is indeed found to be an oblate ellipsoid-as is often deduced from a simplified Sievers model that assumes a pure |±15/2> ground-state doublet for the lanthanide ion. The large equatorial