The synthesis of nanoparticles has received great attention owing to their superior physical and chemical characteristics, as well as versatility. In various fabrication methods, sol–gel, and solvothermal methods are important for synthesizing high quality nanoparticles. This process involves the formation of a colloidal solution that is known as sol and conversion of this sol type into gel phase through chemical processes such as hydrolysis and condensation of metal alkoxides or metal salts. It permits the control of both the particle size as well as the composition, and it is applied to produce metal oxides and mixed-metal oxides with homogeneous characteristics. On the other hand, solvothermal is the process in which the treatment is carried out at high pressure and/or high temperature of solvent to form nucleus and grow the nanoparticles. This method offers insolubility of solvents that can be chosen at will, as well as the synthesis of various materials, including metals, semiconductors, and hybrid nanoparticles. Solvothermal process is capable to provide nanoparticles with precisely defined morphologies and dimensions together with high crystallinity. This chapter discusses on the relative benefits depending on the desired physical and chemical characteristics of the material and the intended application, thus qualifying the two methods as valuable tools in nanomaterials fabrication.