In this report, the simple hydrothermal approaches to the fabrication of porous NiO nanostructures including nanospheres and nanotoroids were described. Morphologies and crystal structure of the as-fabricated nanomaterials were characterized by various techniques such as SEM, TEM, XRD, EDS, and N2 adsorption/desorption isotherm. The results showed that the porous NiO nanospheres have the diameter ranging from 2 to 10 µm, which are self-assembled nanoparticles (NPs). The nanotoroids have an average outer particle diameter and iner diameter are of ~300 nm and ~60 nm, respectively. This simple and mild approach to fabricate highly porous NiO nanostructures could be easily scaled up and potentially extended to the synthesis of other porous nanostructured metal oxides