The development of economical, highly active, and robust electrocatalysts for oxygen evolution reaction (OER) is one of the major obstacles for producing affordable water splitting systems and metal‐air batteries. Herein, it is reported that the subnanometric CoO_x clusters with high oxidation state substitutionally dispersed in the lattice of rutile TiO₂ support (Co‐TiO₂) can be prepared by a thermally induced phase segregation process. Owing to the strong interaction of CoO_x clusters and TiO₂ support, Co‐TiO₂ exhibits both excellent intrinsic activity and durability for OER. The turnover frequency of Co‐TiO₂ is up to 3.250 s⁻¹ at overpotentials of 350 mV; this value is one of the highest in terms of OER performance among the current Co‐based active materials under similar testing conditions; moreover, the OER current density loss is only 6.5% at a constant overpotential of 400 mV for 30 000 s, which is superior to the benchmark Co₃O₄ and RuO₂ catalysts. Mechanism analysis demonstrates that charge transfer occurs between Co sites and their neighboring Ti atoms, triggering the efficient CoTi cooperative catalytic centers, in which OH* and O* are preferred to be adsorbed on the bridging sites of Co and Ti with favorable adsorption energy, inducing a lower energy barrier for O₂ generation.