Cerium oxide is a rare-earth metal oxide known for its exceptional catalytic, optical, and thermal properties. CeO₂ nanoparticles are notable for their ability to create and heal oxygen vacancies, making them excellent oxygen storage materials. Their redox behavior enables both radical scavenging and oxidative catalysis depending on conditions. CeO₂ is applied in automotive catalytic converters, combustion catalysts, energy conversion systems, and protective coatings, and is being investigated in biomedicine as a nano-antioxidant.