Atom probe tomography has been applied to study lithium-induced corrosion of Pulsed-Laser Deposition grown Al2O3, which is a candidate coating material for breeder blankets for nuclear fusion reactors. Coated Eurofer97 specimens were immersed in static Pb-17Li for 7000 h with samples extracted from the regions near the ceramic-substrate interface to determine the extent of Li penetration. Li-enriched regions, which are non-stoichiometric with respect to any known equilibrium phases predicted by the Li-Al-O phase diagram at 823 K, are reported for the first time in Al2O3. The nature and composition of the Li-enriched features were characterized with nanometre resolution. It was found that the Li content inside these features may increase to a maximum of 35 at%, with the adjacent Al2O3 matrix containing approximately 5–10 at% Li. Based on these results, the corrosion mechanism of amorphous Al2O3 is proposed to be Li substitution of Al atoms.