Abstract Atomically thin two‐dimensional semiconductors provide an ideal platform to establish clear structure‐property relationships in the field of photocatalysis. Herein, we fabricated the atomically thin Bi 2 MoO 6 nanosheets by a facile and scalable wet‐chemical synthesis approach. Oxygen vacancies were inevitably induced into the nanosheets as the thickness of the nanosheets exposed interior atoms, which are clearly identified by X‐ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) spectra. More intriguingly, the oxygen vacancies formed on the open interfaces could enhance charge transport, further improving the photocatalytic performance. Benefiting from the large surface areas and increased visible light absorption, the present atomically thin Bi 2 MoO 6 nanosheets display extraordinary high‐performance of photocatalytic degradation of phenol and cycling stability. More importantly, we believe that this achievement in ultrathin two‐dimensional material (atomically thin Bi 2 MoO 6 nanosheets) could bring new insights into designing high‐performance photocatalysts.