The oxygen vacancy diffusion in Al2O3 with a corundum structure is investigated by the projector augmented-wave method within the density functional theory. The O-vacancy formation energy in dependence on the Fermi energy and oxygen chemical potential is estimated. The average temperature-dependent diffusion coefficient by the statistical approach is calculated. It is shown that in the case of neutral vacancy under O-poor condition (upper-bound estimation) the diffusion coefficient is by one–two orders higher than experimental values. The influence of impurities on the diffusion properties of oxygen in the oxide is discussed.