We use computational and experimental methods to study d0 ferromagnetism at a charge-imbalanced interface between two perovskites. In SrTiO 3/KTaO 3 superlattice calculations, the charge imbalance introduces holes in the SrTiO 3 layer, inducing a d0 ferromagnetic half-metallic 2D hole gas at the interface oxygen 2p orbitals. The charge imbalance overrides doping by vacancies at realistic concentrations. Varying the constituent materials shows ferromagnetism to be a general property of hole-type d0 perovskite interfaces. Atomically sharp epitaxial d0 SrTiO 3/KTaO 3, SrTiO 3/KNbO 3, and SrTiO 3/NaNbO 3 interfaces are found to exhibit ferromagnetic hysteresis at room temperature. We suggest that the behavior is due to the high density of states and exchange coupling at the oxygen t 1g band in comparison with the more studied d band t 2g symmetry electron gas.