Two-dimensional(2D) nanomaterials possess sheet-like structures with the thickness of nanoscale, but the lateral size is infinite. In 2004, Andre Geim and co-workers at the University of Manchester successfully exfoliated a sheet of graphene from graphite by the micromechanical cleavage technique, which marked the beginning of 2D nanomaterials. Given the ultrahigh carrier mobility, excellent mechanical property, good thermal stability, superior thermal conductivities and huge specific surface area of graphene, it causes general exploration of other graphene-like 2D nanomaterials.===The 2D feature is unique to access unprecedented physical, chemical, electronic and optical properties. For example, the electron confinement in two dimensions makes them ideal candidates for the fundamental study in condensed matter physics and electronic/optoelectronic devices; the large lateral size endows them with huge surface area and high exposure of active sites. Due to their unique properties, 2D nanomaterials have promising applications in energy storage and conversion, electronic devices, catalytic reaction, sensing and biomedicine. By now, nearly 20 types of 2D nanomaterials have been studied, such as graphene, graphitic carbon nitride( g-C₃N₄), transition metal dichalcogenides(TMDs), transition metal carbides/nitrides(MXenes), layered double hydroxides(LDHs), transition metal oxides(TMOs), Ⅲ to Ⅵ layered semiconductor(MX₄), and perovskite-type hybrids(AMX₃).===In this special issue of the novel 2D nanomaterials, we selected 12 related articles in reviews, research papers and brief communications involving supercapacitor, electrochemical catalysis, sensing, battery, fluorescence, water treatment and antiflaming performance of 2D nanomaterials. We hope that readers will have a deep understanding of the current development of 2D nanomaterials, and find it beneficial to their future researches.===Toward this end, I greatly appreciate the outstanding contribution of all authors, as well as the strenuous efforts from the editorial staff members.