AbstractWe report the catalytic oxidation of organic substrates by a cobalt complex, [CoIII(TAML)]− (TAML = tetra‐amido macrocyclic ligand), and meta‐chloroperbenzoic acid (m‐CPBA) under the mild reaction conditions and the identification of a cobalt(IV)–oxo intermediate, [CoIV(TAML)(O)]2−, as an active oxidant in the catalytic oxidation reactions. In the hydroxylation of cyclohexane, cyclohexanol is the sole product and the hydroxylation reaction occurs via an oxygen non‐rebound mechanism. Kinetic isotope effect value of 3.1, obtained in the oxidation of cyclohexane‐h12/d12, indicates that a hydrogen atom abstraction from cyclohexane by the cobalt(IV)–oxo complex is the rate‐determining step. The catalytic oxidation of cyclohexene prefers the C═C bond epoxidation to the C–H bond activation, yielding cyclohexene oxide as a sole product. In the epoxidation of cis‐ and trans‐stilbenes, cis‐ and trans‐stilbene oxides, respectively, are yielded stereoselectively. The present study reports a highly selective catalytic oxidation of organic substrates by a cobalt complex and m‐CPBA and the involvement of a cobalt(IV)–oxo intermediate as an active oxidant in the catalytic oxidation reactions.