Advanced oxidation processes (AOPs) such as cavitation and ozonation have been used as an alternative and effective option for the treatment of wastewater with difficult to biodegrade compounds. In this review, the necessity and advantages of combining hydrodynamic cavitation with ozonation (HC/O3) were initially discussed. The discussion of the mechanism of the HC/O3 process revealed the presence of both mechanical and chemical effects. Overviews of earlier work with HC/O3 technology were then summarised to show the positive synergies and the HC devices in different wastewater treatments. Recommendations were given for parameter selection by analysing the impact of important operating parameters on process performance. Energy efficiency and cost comparisons indicated that the HC/O3 process was more cost effective than the individual process. Overall, the HC/O3 process with optimised conditions is able to increase the degradation rate of refractory pollutants by more than 40% compared to the HC process alone.