Hydrodynamic cavitation, a newly developed process intensification technique, has demonstrated immense potential for intensifying diverse physical and chemical processes. In this study, hydrodynamic cavitation was explored as an efficient method for the formation of sub-100 nm oil-in-water (O/W) emulsions with high stability. O/W emulsion with an average droplet size of 27 nm was successfully prepared. The average droplet size of O/W emulsions decreased with the increase of the inlet pressure, number of cavitation passes and surfactant concentration. The formed emulsion exhibited admirable physical stability during 8 months. Moreover, the hydrodynamic cavitation method can be generalized to fabricate large varieties of O/W emulsions, which showed great potential for large-scale formation of O/W emulsions with lower energy consumption. (C) 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.