Oxygen in the excited state is essential for organic synthesis and medical treatment. Herein, a novel phenomenon is reported in which the magnetic ground state of molecular oxygen undergoes a transition at room temperature from S = 1 to S = 1/2, corresponding to the transition of O2 from a triplet to a doublet state after stable physical adsorption on the defect‐free surface of bulk VSe2. This density functional theory (DFT) calculations demonstrate the stable physical adsorption of O2 on both 1T‐ and 2H‐VSe2 surfaces without further decomposition. Electron spin resonance (ESR) measurements confirm the spin state transition. Theoretical simulations reveal the charge transfer from entangled V‐3d and Se‐4p bands to oxygen as the leading cause of the spin state transition. This mechanism has not been previously proposed and offers multiple potential applications, from organic synthesis to medicine. Moreover …