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A knowledge of adsorption behaviors of oxygen on the model system of the reduced rutile TiO₂(110)-1×1 surface is of great importance for an atomistic understanding of many chemical processes. We present a scanning tunneling microcopy (STM) study on the adsorption of molecular oxygen either at the bridge-bonded oxygen vacancies (BBO_V) or at the hydroxyls (OH) on the TiO₂(110)-1×1 surface. Using an in situ O₂ dosing method, we are able to directly verify the exact adsorption sites and the dynamic behaviors of molecular O₂. Our experiments provide direct evidence that an O₂ molecule can intrinsically adsorb at both the BBO_V and the OH sites. It has been identified that, at a low coverage of O₂, the singly adsorbed molecular O₂ at BBO_V can be dissociated through an intermediate state as driven by the STM tip. However, singly adsorbed molecular O₂ at OH can survive from such a tip-induced effect …