The effect of doping with rare earth atoms (Sc, Y, and La) on the stability, structural, electronic, and photocatalytic properties of the O-terminated ZnO surface was investigated by using the first-principles method. The obtained results show that all these elements have negative formation energies for all possible values of the oxygen chemical potential, and this means that the doping process with RE atoms (RE = Sc, Y, and La) enhances the stability of this surface. Our results show also that, among all considered elements, the Sc atoms have the lowest formation energy followed by Y and La, respectively. We have also investigated the effect of the formation of a RE-V-o complex on the properties of the ZnO(0 0 0 (1) over bar) surfaces. We find that the formation of a RE-V(o )complex is energetically more favored than the formation of isolated REzn defect under Zn-rich conditions. The effect of the formation of both REzn and RE-V-o defects on the electronic and photocatalytic properties of the O-terminated ZnO surface was studied in details and the obtained results show that the RE-V-o complex may be the origin of the photocatalytic properties enhancement of the doped surfaces. Moreover, we found that the Sc-doped surface prepared under Zn rich conditions may have the best photocatalytic properties followed by Y- and La-doped surfaces, respectively.