Nitrate contamination of groundwater is a global issue that has stimulated significant research interest. Understanding the prevailing processes of nitrate removal from groundwater, influences of process conditions and the performance of various approaches are vital for successfully dealing with nitrate remediation. Natural and engineered processes of nitrate removal from groundwater are discussed with focus on the performance of natural and engineered innovative techniques for nitrate removal from groundwater. Nitrate removal from groundwater can be accomplished through microbial autotrophic and heterotrophic mechanisms in the subsurface under natural and engineered conditions. The application of these processes to in-situ and ex-situ nitrate removal is also discussed in this review. Further, the effect of temperature, pH, electron donor and biogeochemistry on groundwater nitrate removal are elaborated. While natural attenuation processes result in small amounts of nitrate removal from groundwater, engineered processes are able to achieve significantly higher nitrate removal from groundwater. However, the challenges of secondary pollution need to be addressed in adopting these technologies for groundwater treatment for potable use.