Nanoscale metal oxide materials have been attracting much attention because of their unique size- and dimensionality-dependent physical and chemical properties as well as promising applications as key components in micro/nanoscale devices. Cupric oxide (CuO) nanostructures are of particular interest because of their interesting properties and promising applications in batteries, supercapacitors, solar cells, gas sensors, bio sensors, nanofluid, catalysis, photodetectors, energetic materials, field emissions, superhydrophobic surfaces, and removal of arsenic and organic pollutants from waste water. This article presents a comprehensive review of recent synthetic methods along with associated synthesis mechanisms, characterization, fundamental properties, and promising applications of CuO nanostructures. The review begins with a description of the most common synthetic strategies, characterization, and associated synthesis mechanisms of CuO nanostructures. Then, it introduces the fundamental properties of CuO nanostructures, and the potential of these nanostructures as building blocks for future micro/nanoscale devices is discussed. Recent developments in the applications of various CuO nanostructures are also reviewed. Finally, several perspectives in terms of future research on CuO nanostructures are highlighted.