Nanotechnology has successfully gained applications in many areas of life, thereby seen as the modern way of creating products, which results in high efficiency of use. In the petroleum processing industries, this revolution is no exception. The efficiency of a number of conversion processes improves upon application of materials with the nanometer scale dimension, which is caused by improvements and developments of better material properties as the particle size decreases. In this chapter, the applications of nanotechnology through nanocatalysis in petro-refining processes are highlighted. This is exemplified by discussing the applications of nanotechnology in several typical petroleum refining processes, including catalytic cracking, oxidative dehydrogenation of alkanes, and desulfurization. Other processes for the production of clean fuels are also briefly reviewed. The key benefits of “nano-tech” application in catalysis are based on the exposure of a large surface area for reaction, thereby reducing the tendencies to adverse and side reactions. The desire for an improved catalyst with high activity, low deactivation, and low coke formation to meet the growing demand for chemicals and fuels necessitates the increasing exploitation of nanoparticles as catalysts.