Two‐dimensional metal–organic nanosheets (2D MONs) are an emerging class of ultrathin, porous, and crystalline materials. The organic/inorganic hybrid nature offers MONs distinct advantages over other inorganic nanosheets in terms of diversity of organic ligands and metal notes. Compared to bulk three‐dimensional metal–organic frameworks, 2D MONs possess merits of high density and readily accessible catalytic sites, reduced diffusion pathways for reactants/products, and fast electron transport. These features endow MONs with enhanced physical/chemical properties and are ideal for heterogeneous catalysis. In this Review, state‐of‐the‐art synthetic methods for the fabrication of 2D MONs were summarized. The advances of 2D MONs‐based materials for electrocatalysis and photocatalysis, including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO₂RR), and electro‐/photocatalytic organic transformations were systematically discussed. Finally, the challenges and perspectives regarding future design and synthesis of 2D MONs for high‐performance electrocatalysis and photocatalysis were provided.