Catalytic oxidation is an oxidation in which a catalyst mediates electron and/or oxygen-atom transfer from an oxidant to a substrate and is regenerated in the catalytic cycle ^[1][2]. In catalysis and oxidation reactions the concept is bounded by a net increase in the oxidation state of the substrate and by turnover of the catalytic species, whether a metal surface, a molecular metal complex, or a mediator. Essential features are an oxidant (O₂, H₂O₂, or an anodic equivalent), a catalyst that activates that oxidant or the substrate, and a sequence of electron-transfer steps that returns the catalyst to its resting state ^[2][3]. Heterogeneous variants include plasmon-enhanced oxidation at silver nanostructures and interface-confined ferrous centers that activate oxygen at a metal–oxide boundary ^[1][4]. Homogeneous biomimetic systems couple a metal catalyst to a coupled electron-transfer chain so that molecular oxygen or hydrogen peroxide can be used without stoichiometric metal consumption ^[3]. The concept is distinguished from stoichiometric oxidation by regeneration of the oxidant-activating species, and from catalytic reduction by the direction of electron flow. Conceptual limits exclude combustions in which the catalyst only ignites an uncontrolled radical chain and exclude oxygen-atom transfers that do not change the substrate’s formal oxidation state.