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.