ABSTRACTAdvanced oxygen carrier plays a pivotal role in various chemical looping processes, such as CO2 splitting. However, oxygen carriers have been restricted by deactivation and inferior oxygen transferability at low temperatures. Herein, we design an Fe–Ov–Ce–triggered phase‐reversible CeO2−x·Fe·CaO ↔ CeO2·Ca2Fe2O5 oxygen carrier with strong electron‐donating ability, which activates CO2 at low temperatures and promotes oxygen transformation. Results reveal that the maximum CO2 conversion and CO yield obtained with 50 mol% CeO2−x·Fe·CaO are, respectively, 426% and 53.6 times higher than those of Fe·CaO at 700°C. This unique multiphase material also retains exceptional redox durability, with no obvious deactivation after 100 splitting cycles. The addition of Ce promotes the formation of the Fe–Ov–Ce structure, which acts as an activator, triggers CO2 splitting, and lowers the energy barrier of C═O dissociation. The metallic Fe plays a role in consuming O2−lattice transformed from Fe–Ov–Ce, whereas CaO acts as a structure promoter that enables phase‐reversible Fe0 ↔ Fe3+ looping.